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Coding 101 21
Shannon Morse: Today on Coding 101 it is all about Perl, with our new Code Warrior! It's up next...
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Fr. Robert Ballacer: Welcome to Coding 101, it's the TWiT show where we let you into the world of the code monkey. I'm Father Robert Ballacer.
Shannon: And I'm Shannon Morse and for the next 30 minutes or so, we're going to get you all coded up on everything you need to know to be a Perl Code Warrior.
Fr. Robert: That's right and by the way, Perl... So we're not in Python anymore, we're done with the Python.
Shannon: I am so excited about this, I can't wait to get learned up on all of this.
Fr. Robert: Learned up. Now the cool thing about Perl, Shannon is- We covered C# in the first module, right?
Shannon: We did, yes.
Fr. Robert: And that was very structured and it was a compiled language so we had to turn it into a binary before we could actually do anything with it. Then we did Python, which was an interpreted language, right? It was dynamically compiled so we didn't have to worry about running it and making an executable. We're now doing Perl which is also a scripted language, it's like Python. But it's also more structured like C# so we're kind of doing that best of both worlds. It's a very useful language but it's going to borrow elements from both C# and Python.
Shannon: So it's kind of in the middle.
Fr. Robert: It's in the middle, yeah. It's like the little baby bear, you know? Not too hard, not too Pythony.
Shannon: Not too soft.
Fr. Robert: Just right. Now before we do this, of course the first episode of any module has to be, how do they get started with Python? The cool thing about this is unlike C#, they're not going to have to download that huge program from Microsoft to get the visual studio IDE it's not-
Shannon: Can I actually use Perl inside of Notepad?
Fr. Robert: Oh yeah, it's just like Python. Anything you have that can edit text, you can write Perl programs in.
Shannon: So all I need is the distribution so that my computer can actually run these programs, is that right?
Fr. Robert: Exactly and I understand that you are going to tell us how we do that, regardless of whether we're using Linux, Mac, or Windows.
Shannon: I sure am. So if we take a look at my computer over here, I have a website up that is called perl.org and if you go to perl.org/get.html, this is where you can actually download the distribution. You'll notice here that it says Perl is already included in Linux and in Mac OS X.
Fr. Robert: I know okay, I get it. If you run Linux or OS 10 yeah, Perl is already built in and you don't have to do anything.
Shannon: That's kind of awesome. But it might be an older distribution so you might still want to go here and update to the newest version. Also, you'll notice with Windows there is this one called Strawberry Perl and there's Active state Perl. So Strawberry Perl is basically an open-source build of Perl and then there's Active state, which is the one we're going to use for the show today. ActivePerl downloads, you just click the 'Download ActivePerl for Windows' button and then choose whether you're X86 or X64. I'm X64 so I just download this MSI and then I run it and I'm good to go. That's all you have to do.
Fr. Robert: Now I'll say this, I know some people who have really messed themselves up downloading the wrong version. If you're running a 64 bit operating system, download 64 but otherwise, don't. In the worse-case scenario, it will install because it's going to pass the check but then you're going to get funkiness. Perl won't do anything, so do a quick check. If you're using Windows right click on 'My Computer,' go to 'Properties' and it will tell you right there whether it's a 32 or a 64 bit operating system, it will tell you which one to download.
Shannon: And if you're confused about where to find 'My Computer' in Windows 8 like I did you could just go to the search bar and search computer.
Fr. Robert: Or go to our Google+ page at g+.to/twitcoding and you can ask someone there, we promise we won't make that much fun of you.
Shannon: That's true and speaking of our Google+ account if you go over there, you can even show us your code once you get really into Perl. Generally, on the first episode we don't have any viewer submissions that we can share with you but going forward on our Perl module, we'll be able to show different examples that our fans have showed us.
Fr. Robert: Exactly, and that's part of what we really enjoy. Every show and every time we do one of these programming modules, Snubs starts the show by going into the G+ group and by pulling out examples from people who are at all different levels of programming expertise; beginner, intermediate, and expert and we show it off on Coding 101. It's part of the way we can show you what's possible even if we haven't quite gotten there in the lessons.
Shannon: So, you want to get started? I'm pretty excited.
Fr. Robert: I don't know, it's Friday...
Shannon: Oh come on!
Fr. Robert: Okay let's do it. Now, let's talk a little bit about Perl okay? Perl, if you did the first two modules, C# and Python, again it's going to be somewhere in between. It's an interpreted language, it's a scripted language which means I don't have to turn it into an executable, right?
Shannon: Yeah, that's awesome.
Fr. Robert: Because like Python, I can write it in Notepad, I can write it in V, I can write it in Emax. You pick your text editor of choice, and that's what you're going to be writing in and all you have to do is run or script the program in real time and it will tell you whether or not it works.
Shannon: That's so cool, so all I have to do is open up Notepad, write my code, and then save it as a .pl?
Fr. Robert: .pl right. The extension tells the computer that this is a Perl file and that it should be using that extension, or distribution, to go ahead and process what's in it.
Shannon: Got it, cool.
Fr. Robert: The other thing I remember about Perl- And our Code Warrior is going to touch on this. -Is Perl is one of those languages that is absolutely suited for web work.
Fr. Robert: It really is, it really is. It's very good with manipulating data, it's very good with dealing with information that is both going and coming from the computer on the internet so keep that in the back of your mind. As we are doing these lessons, ultimately our Code Warrior is going to teach you how to use this to... I don't know, say, generate forms on a webpage or properly process information that's coming off of a webpage.
Shannon: So is that the reason why Perl was made?
Fr. Robert: No, Perl was made because there was a bunch of geeks who said, I don't like any of the programming languages, I want Perl. That's pretty much how all programming languages are made. Let's get back to- I'm going to start a Holy War and I don't want to do that. The first thing that we want to do when we talk about Perl is we want to talk about the control structure. Remember C#? C# was unique because we could write the entire program on a line, as long as we separated it with semicolons remember? Python was different. Python took white space into consideration.
Shannon: Right, that's why we have to put the tabs and that's why we entered between each line.
Fr. Robert: Exactly. Right, which was important because if you didn't format it right, even if the proper words were there, the proper commands, if you didn't make it indented or if you didn't put it on a new line Python wouldn't know how to deal with it and you'd get an error.
Shannon: I remember that.
Fr. Robert: So Perl, in this instance is more like C# than it is like Python. You need to end every applicable line with a semicolon so it knows that this is a code block and I execute this before I move on to the next.
Fr. Robert: So let's go ahead and take a look at what a code block inside of Perl looks like. Go ahead and switch to 'My Computer' and don't worry if you don't understand everything here, we're going to explain it eventually. Right now what you see me doing is I'm declaring two variables and of course-
Shannon: Numbers and string.
Fr. Robert: Numbers and string, right. I'm filling the numbers variable with 1, 2, 3, 4, 5 and I'm filling the string variable with- This is a string. -I end each one with a semicolon.
Shannon: And I also notice that with the string one you have that in quotes and you start each one with a $.
Fr. Robert: Yeah, yeah we're going to go over that. But this is what the general structure looks like. Now if I wanted to, I could delete the lines. In fact, you're going to see this a lot when you deal with pro programmers, especially obnoxious pro programmers. They tend to like to write everything in a line.
Shannon: Oh my God that would drive me nuts.
Fr. Robert: Yeah.
Shannon: I like the organization.
Fr. Robert: I like the organization. But you don't need that. You could write this on a line but please, please just follow best practices and keep it nice and easy to understand. Alright, now that you've seen the basic structure and what it looks like, and hopefully you've made the comparisons to C#. Let me actually show you what I've done here. If you come back to me, what we're going to be doing is we need to first show you how you work with variables in Perl.
Shannon: Yay, variables!
Fr. Robert: Okay, now...
Shannon: Please tell me it's easy.
Fr. Robert: It's so easy. Do you remember back to C# when we had to declare variables of a certain type so-
Shannon: Yeah, you had to say if it was a string or an integer or whatever.
Fr. Robert: All those good things. So you had to specifically say at the beginning, before you started doing any expressions, these are my variables and these are the variable types, right? That's part of C#. Then we got to Python and Python- I didn't have to tell you what kind of variable it was.
Shannon: It just knew.
Fr. Robert: It just knew right? It does context and also, I didn't have to declare all of my variables in the beginning, I could do it in the expression. As I need the variables, I just put them in there and Python just allocates memory.
Shannon: Which I really liked.
Fr. Robert: Which is nice, because Perl, even though the structure is more like C# the variables and declaring the variables is more like Python.
Shannon: Oh I like this so far.
Fr. Robert: Right so I don't have to declare a type or all of the variables at the beginning, I could just use them as I write the expressions and it will be allocated within Python.
Shannon: I'm excited now.
Fr. Robert: Yeah, and when we talk about variables in Perl there are a couple of different types. Most notably, there are scalers, there's arrays, there's associative arrays, and there's hashes. We're only going to talk about the first two. Let's not get confused, we're talking about scalers and arrays.
Shannon: Okay, what is a scaler.
Fr. Robert: A scaler, quite simply is like any other variable that you've written in Python to hold a string or number or a character.
Shannon: Oh okay.
Fr. Robert: These are either numbers or strings. They don't require you to mark the variable as a number or string it all looks the same to Perl and it actually will infer from context what kind of variable it is. So for example, if I put something in quotations and write a sentence, Perl will figure out that's a string. If I write 1, 2, 3, 4, 5 Perl will figure out that's an integer.
Shannon: Wow, that's easy.
Fr. Robert: If I write 3.14 Perl will figure out that's a real number, it's a float. Perl also doesn't require you to differentiate between integers or real numbers, which is nice and we'll get to that later on. But when I use scalers all I have to do is I have the name of my variable- So let's say var1, and right before the variable, I put a $.
Shannon: Why do you put a dollar sign?
Fr. Robert: Because that indicates to Perl that this is a variable.
Shannon: Oh okay so that's it's indication.
Fr. Robert: That's it's indication, whatever is connected to this $ is going to be my variable, that's my variable name. That's both how I declare it and how I call it. So if I call something "$var1" anytime I want to use var1, I have to proceed it with a $.
Shannon: Oh I see.
Fr. Robert: Okay so just remember that. Consider that part of the name, it's not var1 it's $var1 right. Now if you go ahead and let's go ahead and go back to my computer, here you see I have created these variables, numbers-
Shannon: That's why you have the $.
Fr. Robert: Right. This is $numbers and this is string. This is actually the name and $numbers I fill with 1, 2, 3, 4, 5 and $string I fill with, This is a string. Now you remember how we printed in C#? The see out, and there was a function call and it was kind of-
Shannon: Print line...
Fr. Robert: Yeah, and Python was a whole lot easier, right?
Fr. Robert: Again, this is where Perl is more like Python. This is what printing looks like, print. You just print and then you could either put the name of a variable, you could put numbers, or you could put something in quotations, which is a string.
Fr. Robert: What I've done here, this is a unique piece and it's different from Python so you got to remember this. I've put, print = "This is me printing a String: $string/n";
Shannon: So even though you're putting that inside of quotes, it knows because you've got that $ that you're not telling it to print $string, you're actually telling it to print-
Fr. Robert: The variable string, right. And then I do it again for this one; print = "This is me printing a variable with numbers: $numbers"; So by putting $numbers, it knows to go ahead and print the value of the variable numbers which is 1, 2, 3, 4, 5. Now this, <STDIN>; is just the standard input, just like in Python-
Shannon: So it's like enter?
Fr. Robert: Right, it's waiting for input from the user and then the character turn, the enter key. The reason why I'm going to put this at the end of my program is because I don't want the window to close. Because otherwise it would just flash. So this is going to wait for me to hit enter before it closes. Now if I run the program, because I've got Perl installed on this, it'll just do this, This is me printing a string: This is a string
This is me printing a variable with numbers: 12345 and each time it is going to go ahead and print what was inside that variable and now it's waiting for me to hit enter. That's it.
Shannon: Pretty obvious.
Fr. Robert: Pretty obvious, very simple. I'm going to hit enter and it's going to close the window.
Fr. Robert: Okay so, in that sense, printing and playing with variables in Perl is pretty darn easy, there's not a whole lot there and it is basic. Hopefully if you've watched any of the other modules, especially the Python module, this should be an old hat right?
Shannon: Definitely. But of course, if you haven't watched any of the earlier modules, definitely go back and watch them because they're super useful. Especially the first module because we defined a lot of the terms that we're using now like variables, integers everything like that.
Fr. Robert: Right. I want to show one more thing, if you'll go back to showing my screen, remember how I told you how you don't have to declare what type of variable you were printing right? This is a really good example of that. So it knows that here, I'm creating a scaler variable because I've put a $. And I've called it var1, var2, var3 and I'm filling it with an integer, 28. I'm filling it with a string, 'Coding 101' and I'm filling it with a floating 3.14. Nowhere have I declared that the first is an integer, that the second one is a string, and that the third one is a floating point.
Shannon: Yeah, you just put them in.
Fr. Robert: Which is nice. This is really how I like programming to be done, where it can figure out what I want. I'm just going to go print them out print Var1, print Var2, print Var3. The little \n thing after the Var1, 2, and 3 commands-
Shannon: That just tells it to enter to a new line at the end of that line of commands.
Fr. Robert: Right. If you go to a Perl start-up document, you're going to see that it gives you a bunch of control characters. You could add a new line, you could actually append to the line, \n just says drop down to the next line. So if I run this it will look just like this. It's going to
and then it's going to print those three and so I then, get
Coding 101 and
Fr. Robert: Easy peezy lemon squeezy. Nothing to it, right?
Shannon: Okay, I'm ready to move on.
Fr. Robert: Let's move on to the slightly more complicated but not much more complicated arrays. Arrays are sort of like in Python what we did with lists. So what I have is the name of an array and it has an index. That index tells me what element within that array I'm dealing with. Here's something unique about Python. When we're talking about an array in Python, we're talking about a one-dimensional array. It's just a list of elements that belong to that array.
Shannon: Just a list, that's it.
Fr. Robert: Just a list. We can go to more complicated data types later, but right now we're just dealing with that one-dimensional array. Now, this is what it looks like when I use an array if you'll go back to my screen I'll show you. Notice how this character is different.
Shannon: Whoah, that's a lot of stuff.
Fr. Robert: What did I use for declaring a scaler variable?
Shannon: Oh why is there an @?
Fr. Robert: Yeah, it's different. So when I'm in Perl, if I use a $ it's declaring that I'm using a scaler variable. If use an @ it means I'm declaring an array.
Shannon: Oh okay.
Fr. Robert: And just like in Python, what I've done here is I'm declaring this array called C101 and then I'm filling it with three values; Padre, Snubs, and Brian. So three different values, or three different strings go into that array called C101.
Shannon: Ah I see, okay. So each one is a separate string.
Fr. Robert: Each one is a separate string, but they are all part of that array. The way I can prove it to you is I have right below it it says as follows, print "Here are the values in the array 'C101' :\n" ; So look at the print.
Shannon: It's the $.
Fr. Robert: It's the $, right. Because you can think of an array as an array of scaler variables. So even though it's an array, each element itself is a scaler variable.
Shannon: Oh that's cool.
Fr. Robert: So you see how this kind of works. So if I have an array called C101 with three elements; Padre, Snubs, and Brian what that really means is that I have three scaler variables. Each one would be called $C101 and then in the brackets, either 0, 1, or 2 because remember we start at 0, right? Those are my three scaler variables inside that array. So when I hit this what it should do is it should say, Here are the values in the array and it should say Padre Snubs and Brian. So let's go ahead an run it, and you'll see it like that. Padre Snubs and Brian.
Shannon: It works!
Fr. Robert: It works, and this proves to you that the array is just three scaler variables.
Fr. Robert: Or as many variables as you put into it. If I had put twenty values in there, we would have had twenty scaler variables.
Fr. Robert: Alright so let's look back at the code because it actually continues. What we have here is- This is kind of cool.
Shannon: Whoah, what's going on here?
Fr. Robert: So I've created a new array called @coding and @coding is equal to @C101.
Shannon: So the first array, the @C101 is equal to that coding array.
Fr. Robert: Exactly. It means that the coding array is going to create an exact copy of @C101 array.
Shannon: Why would you do that?
Fr. Robert: Well because sometimes I want multiple copies of the same array. Like for example, remember when we were doing the sort in Python?
Fr. Robert: What we wanted was the original array and the sorted array because the sorted array was going to change. Well this is a very nice way to do it because I can create an array that is just an exact duplicate of another array and then I've got a copy so when I do something to it-
Shannon: It's a copy, it's not deleting the original array.
Fr. Robert: Right. So going back to my code, what I'm going to do after this is I'm going to say the values of the array Coding101 have been copied into the array, Coding. And then I'm going to print the values of the array, which would just be Coding0, 1, and 2 so let's go ahead and run that.
Shannon: So that would just print the same thing over.
Fr. Robert: Right, exactly. So go ahead and zoom in on that Bryan because I know you're like Superman like that. So when I hit enter, it's going to print me the values of the coding array but it'll be exactly the same since I just duplicated it. And boom. Easy. Let's go now, to the last step. There's one more step before we say goodbye to arrays and that is that we need to change an element in the array.
Shannon: Ahh! You're confusing me...
Fr. Robert: Wait, here we go. We already know that an array is just a list of scaler variables, right?
Fr. Robert: And we know how to print individual scaler variables, right?
Fr. Robert: We also know how to assign individual values to scaler variables, go back to my screen and you'll see it right there. What I've done is this... There's the array called C101 and the scaler variable for the third element, which actually is number 2 is going to change to, cranky hippo.
Shannon: Oh, so you're just changing the second... What was it called again?
Fr. Robert: The element. It's actually the third element because of the 0 on the first. So when I print this, now it's going to show me this... In the meantime, the array, coding stays the same.
Fr. Robert: So yeah, after it prints the changes made it will print the original array that we made a copy of.
Shannon: Oh, that's easy!
Fr. Robert: I went over it really quickly, but just remember-
Shannon: But I get it.
Fr. Robert: Yeah but the nice thing about this is Perl is very good at making your data types easy and the array is just an array of scaler variables so how do you refer to an array? You refer to it with the @. How do you refer to scaler variables?
Fr. Robert: So if you are referring to the elements inside of an array, which are just scaler variables, you refer to them with the $.
Shannon: Cool, okay.
Fr. Robert: If you're confused right now our Code Warrior is going to clear all of this up. Now Shannon, before we go to the Code Warrior, I'm thinking that maybe- I feel like I want to hear a little something something about a company that might help me to present my ideas. Like for example, the lesson that I just did.
Fr. Robert: Thank you SquareSpace.
Shannon: We love you!
Fr. Robert: We love you. Now this is the time of the where we're supposed to introduce our Code Warrior but unfortunately we couldn't find one.
Fr. Robert: Yeah, we couldn't find one in the internet but what we did was we found one here at home.
Fr. Robert: Ladies and gentlemen we welcome to you, the latest and brand new Coding Warrior in a line of code heroes, Mr. Patrick Delahanty. Patrick, thank you very much for being our Code Warrior.
Patrick Delahanty: Oh my pleasure, I've been looking forward to this.
Fr. Robert: Now we asked you- Obviously you were an easy choice for us because we work with you every day that we're in here but also because you program Perl for a living. You're not just an instructor.
Shannon: Oh is that what he does here?
Fr. Robert: Yeah, that's what he does. That little office over there, that's all he does all day.
Patrick: I've been doing Perl since like 1985, 1986. I've even got a Perl book by Randall Schwarts that is copyright 1996 and it has a menu in it from 2002.
Fr. Robert: Which by the way folks, there were a lot of you who were saying we should get Randall Schwarts for Perl. We will have Randall Schwarts for Perl when we start getting to 102 but we didn't want to use him for the basic stuff because that's... He's, he's Randall Schwarts.
Patrick: Yeah, I bow to his knowledge.
Fr. Robert: He's like a Code Emperor. He's not a Code Warrior. But Patrick, so you've been telling me for the longest time that I've got to get into Perl and that if I love Python, I'll love Perl and if I get C#, I'll get Perl as well. But why did you get into Perl in the first place?
Patrick: Well I started learning Perl when I worked for internet.com and we were doing websites that needed dynamic back ends and dynamic pages so we used Perl to create the CGI scripts that would present all of the data to the users. It was so easy to pick up and it's just like a natural language because of how you could think about, oh I want it to do this. And that's how you would structure the statements.
Fr. Robert: Yeah. I will say- Thank you for doing this. -I understand that you really kind of you pulled back the original slate that you gave to me that you really wanted to cover with the Coding 101 audience, was maybe a little ambitious.
Shannon: It was over my head.
Fr. Robert: Yeah it was one of those things that's like, that's not 101 Patrick so thank you for- I'll say it. -Kind of dumbing down your lessons a little more.
Shannon: For me.
Fr. Robert: You wanted to introduce us to a few things that you think our Coding 101 monkeys should bring home and play with. You want to introduce us now?
Patrick: Yeah, we're going to start off with just more about the strings and other variables and so I've got Perl on my Mac here, didn't have to install anything.
Fr. Robert: Okay yes, yes I know...
Patrick: I can use Notepad or Text Edit or anything, BB Edit or whatever really. But what I'm going to do here is bring it up in the terminal and so I'm in the terminal.
Shannon: What...? Easy.
Patrick: And this is- If you know Unix commands like LS and everything, that's all in there. So I've got my files here and I'm going to use Emax as my editor just so I can have it all on one screen. With this program, you can see that I've also demonstrated some comments, which all you have to do is put the number symbol at the beginning of the line. Now, at the start of my file, which I didn't see in yours I tell Perl where it is.
Fr. Robert: Right so with this, when we start moving into actually moving our assignments into the web we will always have to have that line because that line is what's going to allow whatever's reading it to understand where this particular piece of code should go. We didn't have to do it on ours on Windows because we were running it straight in a Perl environment. But eventually, we will want to include that in there.
Patrick: And when I've done Perl coding on Windows servers I've had to put in the C: and all of that. So what I've done here is I've made an array that has seven of our shows, the first seven listed alphabetically. And you can see that the spacing doesn't matter. I've put it all nicely formatted.
Fr. Robert: Right. But you could have that all in one line if you wanted to be a jerk about it.
Patrick: Yeah I've got commas between them all here and then close it. Then I've defined our network name and our network equals twit. Then I've picked a number, so I've selected the number 3 and my print statement is simply, subscribe to, and then the content of that array with this number. So I didn't put the actual number in the print statement.
Fr. Robert: So yeah, just like when we did the statically defined element number. What you've done is you're saying the array called 'shows'- But we're addressing a single element so of course we're looking at it as a scaler variable. -Use the scaler variable called 'selected' to tell me which element I want to look at.
Patrick: Yes. And so I could easily change that variable, maybe there's some outside thing that would select a different value and it would print out a different show name. And so you can probably predict what this is going to print out when I run it. So let me exit out.
Shannon: I know!
Patrick: Perl episode 1...
Fr. Robert: And while you're typing that we've got some great questions in the chat room, DoctorMorgiss wants to know what the dollar signs mean. It's just scaler variable, any scaler variable uses the $. And someone asked, wait you can put the variable names inside of quotations? Yes you can, that's one of the cool things about Perl, you don't have to end the string, put the variable in and restart the string. You just drop it in there. As long as you've got that scaler variable indicator at the front, the $, it knows to print it.
Patrick: Yeah, there's so many different ways to do things in Perl and I'll show off a couple different ways to print in a little bit but here, I've executed it and it says, "Subscribe to Coding 101, a fine TWiT show!"
Shannon: Aw, that's cool.
Patrick: So let's go back in and what I'm going to do here is that something to keep in mind is that Perl is case-sensitive. So if I put network equals frog pants and then network equals adequate.com, which one do you think it'll print out?
Shannon: It'll still print out the first one, TWiT, right?
Patrick: Yes, because it is case-sensitive so they're treated-
Fr. Robert: You've actually got three different variables there.
Patrick: It still says, 'A fine TWiT show!'
Shannon: So it's just ignoring the two other variables?
Patrick: Yeah, they're treated as completely separate. So that's tricky when you're coding things- There have been so many evenings where I have been trying to figure out why this isn't working and then I'm like, oh this one has a capital letter and this one doesn't. So it's a little quirk with Perl but-
Fr. Robert: But that's to be expected, I mean, at this level if you're coding then you need to pay attention to capitalization.
Patrick: Yes. Now let me go into another example here. In this one I've got two different ways to print. So it's similar to what we mentioned earlier. There's the original way, which is on this first print line. But on the second line I've actually ended the quote, I've put in a period, put in the variable name, another period, and then continued it. But this is helpful if you have- Let's say there is a variable and you wanted the word to begin right after it so it's like how else would you say, hey separate these two.
Shannon: So that way Perl knows that's not the entire name of the variable and that should be separated.
Patrick: Yes, so if I wanted it to end right here, I could do this and take the space out and then it would print the variable with no space. But if they were together like this, it would think it's a different variable.
Fr. Robert: Yeah it would actually think you were talking about a variable called 'networkshow,' which it doesn't have a value for at the moment.
Shannon: That's good to know. Okay.
Patrick: So now let's execute this, it prints the exact same thing with two different print statements.
Shannon: Cool, I like it.
Patrick: Now I actually have a crazier example here because you might wonder, well what if I want to print something that has quotes in it?
Fr. Robert: This always gets people, when they start putting punctuation- Especially when something comes up where they want to print a $ and they don't want it to think that you're calling a scaler variable.
Patrick: Yeah, so here I've put quotes around this but I can't just put a regular quote because if I do that, it's going to be like, oh you're ending the thing but then it crashes into this so I escape it by putting the backslash before the double quote. Down on this line, I've done the same thing but it's still separated. Here's another way to do it but you'll see the output is a little different for this line here. Where I have the single quote and I didn't have to escape this because there's no double quote at the beginning.
Fr. Robert: Oh, Maxwave wants us to explain escape. Maxwave, when you escape you're essentially telling the compiler or interpreter that's going to be looking for this code not to execute this next part. Don't execute this, this is actually a regular part of the string and I'm not telling you to do a command. If you didn't do that, Perl would think that you're ending the string and then it would look for something else to execute. The escape escapes out of the end of the string.
Shannon: So you're telling Perl, no really this is what I meant to do.
Fr. Robert: Yeah, I just want you to put this, don't mess with me.
Patrick: So on this fourth print line, I've got still the single quote but I've separated it out just like the second one. I ended the quote here and started this variable. So 4 and 2 are very similar but 4 has the single quotes. And then this fifth example here gets a little crazy. Because I'm telling it to print until it sees EOF.
Shannon: What is EOF?
Patrick: End of file. It will print until it sees that so I can actually go in and put in returns and hey this is even more- And as long as this EOF starts on a new line...
Fr. Robert: Now Patrick, I will say what's interesting about this is, this is a very simple example- This was designed to help our users figure out some of the concepts we just gave them but the fact that you're using EOF tells me that you're pulling from your experience of pulling external data files. Eventually this technique could be used to pull from a file that's not on the computer. It's not even on your network, parse it, get the information out of it and then do something with it.
Patrick: Absolutely, but let's not get ahead of ourselves here.
Fr. Robert: Let's not get ahead. But in case people were wondering what the EOF was for, that's what you would use it for.
Patrick: And so let me exit out here and we'll run this to see the difference here. So yeah, this is the second line, it did the same thing as before. Now the third one, presents this and this had the single quotes around everything and it did not interpret this variable or the network variable it just printed it. It didn't care if there were variables.
Shannon: Yeah, it took it literally.
Patrick: Yeah it just went and printed it so, it ignored that. Even the new line, that's why it's all run together here.
Shannon: Got it.
Patrick: It's like I don't care about all this other stuff, I'm just going to put the text there.
Shannon: So quotes make a huge difference in Perl.
Patrick: Yeah, now this one is the fourth one. Because I separated out this variable, remember I ended the single quote, had the variable name, and then started it back up. It actually interpreted that. So even though this part is in single quotes, this part was not so it prints the value. Now here's the start of the final example, the EOF example. You can see it does the new lines, it does everything, it doesn't care and will put in all of the values so this is very helpful, especially when I'm presenting this as webpage content. Like if I have to do a big chunk of html, rather than having to escape all of the quotes and any of the $ and all of this other stuff I would have to worry about, it's a whole lot easier to just do the EOF method and put in a big chunk of text.
Fr. Robert: Patrick, thank you. Thank you very much. I think that might be good for the first episode, give people a good taste and feel. Although we do have a good question from DanS in the chat room and that is, what's the craziest thing you've done with Perl recently?
Patrick: Oh me, let's see... Yesterday, I did a thing that interfaced with a URL shortener so that we can make a bunch of short URL's for TWiT. So you can go to twit.2/c101 and it redirects to Coding 101.
Fr. Robert: Of course, that's what you do with Perl. You do useful things. Patrick Delahanty, our Code Warrior, can you tell the folks where they can find you like your Twitter address or your website, where should they find out more about you?
Patrick: On Twitter, I'm @PDelahanty and my website, enemycodes.com is coded entirely in Perl. Except the forums, which I didn't code, but everything other than the forums is all Perl.
Shannon: That's awesome.
Fr. Robert: And we thank you very much, we will see you next time when we need to call on our Code Warrior.
Patrick: I look forward to it.
Fr. Robert: Shannon, that's a lot for the first episode I think.
Shannon: I have a lot to work with.
Fr. Robert: You have a lot to work with. And we want to give our audience a little bit of time to flex, for many people who already have a coding background, I know this is really simple but please bear with us this is what we have to do. We always want to reach out to the people that have never coded before.
Shannon: I'm glad we do because a lot of times, the first episode is what gets me excited about a language because I'm like, oh I really can do this yes! That was easy to download.
Fr. Robert: Your takeaway should be it's very easy to work with variables and it's very easy to print. Those are two very important things and we just gave it to you.
Shannon: Done and done.
Fr. Robert: Done and done. Now if you want to find out anything about anything that we talked about today, you've got to go to our show page. There you'll find the episodes and also our GIT hub, right?
Shannon: That's right we put all of our code in our GIT hub and we also separate them out by modules so you can easily find every single piece of code that we show in our episodes. We're also on iTunes if you use iTunes for all of your RSS feeds, or podcasts, definitely subscribe to us over there and share it with your friends if you think they would be interested.
Fr. Robert: That's right and if you want to get more involved, as we mentioned at the beginning of the show you've got to join our G+ group. Drop in at g+.to/twitcoding. You're going to find a vibrant community, over 1,000 people who are at all levels of programming expertise from the noobs to the super, super gurus. So if you've got a question, you want to answer some questions or, if you want to show Shannon the code that you wrote that you think we should show off, that's where you go.
Shannon: Definitely and I'll be sharing my own code on the episodes as well. Of course, if you aren't on Google+ and you're like, oh I don't like social networks I'm on Twitter. We're also on Twitter and we're on there pretty much constantly so you can find me @snubs.
Fr. Robert: And I'm @padresj. I'd say until next time I'm Father Robert Ballacer.
Shannon: I'm Shannon Morse. End of file.
Fr. Robert: End of line. Do you want to do a podcast?
Shannon: Do you want to make a program? Everyone programs with me, do you want to make a program? Let it code, let it code.