This is the start of a series of articles that I will be writing for perl. I will start with some basics and progress from there. The end of the road should will get us into using various modules to aid in automation of tasks.

In the Beginning God created the Heavens and the Earth.   He created light to separate the darkness, and called light Day and dark night.  On the Second Day, God created an expanse between the waters, and called the expanse sky.  On the Third Day, God created dry ground which he called land, and the separated water below the sky, he called seas.  God then called out for the land to produce vegetation of all kinds.  On the Fourth Day, God created lights in the expanse of the sky to separate day and night, and let them be used to as signs to mark seasons, days and years.   God made a greater light to govern the day, and a lesser light to govern the night, and stars to fill the expanse.   On the Fifth Day, God created living creatures in the seas and the skies.   On the Sixth Day, God created living creatures on the land, and created man in our image.  On the Seventh Day, God rested from all his work.

On the Eighth Day, God created Perl to aid man in all their repetitive tasks.   …….   Well maybe not, but some might argue it is not that far off.   So, welcome to Perl Snips!   I am hoping to do several of these little articles, kind of like series.   I will start off with just some basic stuff, but I will start branching out to actual code sniplets to do things like ftp, email, various windows queries, etc.   I am not sure how often I will create these articles, but I will endeavor to make one every few weeks at least.   If you have any questions or comments, you can feel free to register for an account and post in the forums.   So now as they say, “On with the show”!

Where to start, Where to start …. I guess we will just jump in with both feet and hope we don’t hit the bottom.   Perl is a interpreted language.  This explains why you must have perl loaded on the system in which you are executing the perl code.   However, you can compile a standalone executable to run on systems that do not have perl, which might be confusing at first.   However, the simple answer is that the libraries and perl interpreter is bundled in side the executable itself.  I typically do most of my Perl to interface with Windows Systems.  Because of this, I use ActiveState Perl for most of my development needs.   If you have never used perl and are a Windows junkie, then by all means, download and install ActiveState Perl for your enjoyment.   Otherwise, other systems such as linux, typically have perl already installed as part of the system.   However on Linux, you may find some modules not “pre” loaded.

So, now on to the fundamental basic syntax and structures that you will need to know as you script with Perl.   First off, perl uses a semicolon as a line terminator.   This is just a mechanism that tells perl that you have completed an instruction that needs to be performed.   As you can imagine, your code will contain a lot of semicolons.   Also, the most typical error you may encounter running a new perl script is a missing semicolon.   Next thing to mention is that perl uses a hash or pound symbol as an indicator of a comment.   Any text to the left of the hash would be considered a comment and not actual code.   The comment extends to the left until an end of line (return/enter) is encountered.

Moving right along, we should discuss the three basic variable types that you will encounter in perl.   The first one is called a scalar.   This variable type can be used to store numeric or string values.   This is a little different than other languages that require you to define a variable to be of a certain type.  In perl, you do not need to define what type of variables are used.  You just simple store the value and perl takes things from there, well almost.  Perl uses a prefix to let it know what type of variable is being used.  This means that a scalar could be defined as a number, and later be assigned a non numeric value.   However in both cases, you will prefix the variable name with a dollar sign ($).   As far as the variable names go, I would suggest using a bit longer names for easy reading and later troubleshooting.   Below is an example that will show you a comment, and some scalar variable assignments.

# This is a comment
$number = 1;
$string = "Hi there";
$another_string = 'What is this about';

You will notice that I showed you two different string assignments.  In perl, you can use either a pair of ” or a pair of ‘ to wrap around your string variables.   The main difference between them, is that the ‘ is an explicit string quote.   This means that what ever you place in between the ‘ is exactly what will be in the string.   We have not got far enough show a lot of the reasoning for this yet, but the following example should get you a general idea.

$number = 21;
$string = '$number';
$string2 = "$number";

From this example, the $string variable will actually contain the characters $number, however $string2 will actually contain 21.   The double quotes allows perl to interpreted variables that are included in the string.   However, the single quotes are an explicit string and perl will not try to interpreted anything inside of the quotes.   So, the biggest thing I would say for you to remember about scalar ($) variables would be this:   A scalar variable contains a single value.   This is to say that a scalar can be a number, a string, etc, but it can not be a set of number or a set of strings.    Which leads me to the next variable type to discuss which is the array.   Arrays are prefixed with an @ symbol.  An array is an ordered set of elements, in which, each element contains a value.   In perl, the ordering of the array begins with 0 in stead of 1.   Whoah, hold up what are we talking about.    Well, lets take a look at an array definition.

@array = (1, 2, 3);

In this example we have defined an array @array and placed three elements which have the values 1, 2, and 3 respectfully.   Now, you can see how arrays can come in handy for storing more information in the variable than a bunch of scalar variables, however, how do you reference a single value in the array?   This is where the ordering that was mentioned above comes in to play.  Remember that we use a dollar sign to tell perl that the variable is a scalar type, and that a scalar type is used for a single value.  Now as far as getting to a single value in the array, we will use a scalar prefix on the array variable, but will also need to add a special suffix to pass in what element we are wanting to access from the array.  For this we use a pair of square brackets to pass in the index value.

$number = $array[1];

This example would assign the value of index 1 of the @arrary, which is 1 right?    Nope, remember that perl uses a starting index of 0, so our example actually assigns the value 2 to $number.   Arrays, can contain a mix of different variable types for each element.   This means you can have arrays of pure numbers, pure strings, mix of numbers and strings, or even other arrays or hashes.   Whoah, you just lost me there, what is a hash?   Are we talking about comments?   Okay, I kind of leaped to something else, but just hold that thought for a moment.   There is one other thing that I want to comment about on arrays.  Something that is pretty common when dealing with arrays is the need to find out how many elements are contained in an array.   This is simple with perl.

$number_of_elements = @array;

In perl, when you assign a scalar variable to the value of an array, perl actually returns just the total number of elements to the variable.   Remember that a scalar is only a single value, which makes this a bit easier to digest.  Now you will also want to keep in mind that the order starts with 0, so you will want to remember that the last element in the array is N – 1.  So our $number_of_elements would have the value of 3, but the last element is actually in index 2.   Now, the thought that you are holding on to from earlier, let me start explaining to you.   In perl our third basic variable type is a hash.   The prefix for a hash variable is noted as a percent symbol.   A hash can be thought of as an array that you are allowed to define your own indexing.   This becomes really handy for pulling values out of the hash.  If you compare a hash to an array, you will see a lot of similarities.

%hash = ('element1' => 1, 'element2' => 2, 'element3' => 3);
@array = (1, 2, 3);

The array is ordered and index 0 – 2, however, the hash has an index of element1, element2, and element3.   Those names can be anything you want them to be.   Now, just like an array, we can use a scalar prefix to the hash variable to retrieve a single value.  In arrays, we used a pair of square brackets and the index value as a suffix.  However, in hashes we will use a pair of squiggly brackets with our index value, but will will also use a -> between the variable and the squiggly bracket.

$number = $hash->{'element2'};

This will get the value from elevemt2 and assign it to the $number.  Just like arrays, hashes can contain numbers, strings, arrays, or even other hashes as element values.   At this point it is worth noting that things can get a little out of hand.   For example, you could define a hash that contains an array which contains hashes that contain hashes, that contains arrays of strings.   The variables can be used to create very complex data structures, but be sure to not over complicate things.

Now a few more things that are common for all of the variable types.   First off, I need to let you all know that perl is case sensitive on variable names.   That is that $number is not the same as $Number or $NUMBER.   All of those variables would be different and not linked to each other in any way.  So when you create your variables, just make a mental note about this.   Also, in other languages, you made have heard about local and global variables.   Perl by default uses global variables unless you explicitly define a variable to be local.  The basic idea is that you can create a $num variable in one area of your program, but $num in another area of the program would be separate and different.   That is to say, by using local variables you can have many $num variables and they could all contain different values, but the local variables are only in memory for the portion of code that are local to.   I will explain this more as we go into other Perl Snips Articles.

For a lack of a better place, I want to let you all know that perl as a command that allows you to terminate your programs.   One way is to use the exit statement and the other is to use the die statement.

exit;

Now the die statement is used a lot more with if statements.   Which we will cover a little later, but right now, you can just sit back and absorb this information, and when ready feel free to jump to the next page.

This is a pretty short and sweet section.   This should not take much to cover and go though.  The basic and most common math functions are available for use.

$num1 = 5;
$num2 = 2;

The first would be addition:

$answer = $num1 + $num2;

This would yield the expected value of 7.   Next we have subtraction:

$answer = $num1 - $num2;

This would yield the expected value of 3.   Next we have multiplication:

$answer = $num1 * $num2;

This would yield the expected value of 10.   Next we have division:

$answer = $num1 / $num2;

This would yield the expected value of 2.5.   Next we have exponents:

$answer = $num1 ** $num2;

This would yield the expected value of 25.  The last item to cover is modulus.  This basically returns the remainder of a divisional operation.   I use this most of the time to alternate between row colors in reports.   I would set up a counter variable that keeps track of the line I am on, and then do a modulus on the counter with 2 to determine more or less even or odd.

$counter = 10;
$color = $counter % 2;
$counter = $counter + 1;
$color = $counter % 2;

The first time around $color would be 0, but the second time around there would be a remainder since it was not an even division.   I use this will other programing statements to achieve the alternating line color.

That wraps up the basic numerical operations, so we can continue on to the next item on our list.

So, we know a lot of different things, however, we still have not done the traditional “Hello World”.   So lets talk about outputting information to the screen.   In perl, we use the statement print followed typically by a pair of ” or ‘.

print "Hello World";
print 'Hello World';

Just like we saw in scalar variables, the single quotes are explicit for printing as well.  This means that using double quotes we can print the values of variables to the screen.

$string = "Hello World";
print "$string";

Now what if we want to print an element from an array or hash.   Well you can just place the variable inside the double quotes, but it is better to place them out side.   This will require us to append strings together or concatenate.  In perl you can use a period to achieve this task.

$string = "Hello";
print $string . " World";

You can do this for arrays or hashes.   However, you can also add just plain strings to each other as well.

print $array[0] . " " . $hash->{element1} . "1" . "2";

The next thing we will cover on the basic print stuff will be just a few special character escape sequences.   In perl we can escape things with a back slash ().   From what we have already talked about, we know that using a $ inside of a double quote string would make perl try to bring a scalar value into the string.

$string = "Hi";
$string2 = "$string";

However, if we wanted to actually have a $string as the value we can use single quotes or escape the dollar sign.   By escaping we are telling perl to do something special.   In the case above if we where to use “$sting” we would get the same results as using single quotes with out the escape.   Now, just as we can escape the dollar sign to tell perl we just want a dollar sign in a double quote, we can use the escape and certain characters to cause perl insert some special characters.

print "Hello Worldn";
print "Hello Worldr";

In this example, the n is a windows style carriage return, and the r is a unix style carriage return.   This is something that you will use a lot.   Also, one other that I will fill you in on is the t.   This will insert a tab into your string.   This is handy for creating tab separated values in reports and so forth.

The next article, we will continue learning more about perl.

T

his is a Captin Kayla Star Date ….. Whoah, Did I just say Star Date?   Not sure Kayla knows what a Star Date is nor would she care.   She has more interest in her feet lately than most anything.  Kayla was as most would suspect spoiled during Christmas, and as you can see, enjoys her Command Center of Fun.   However, most dolls you ask about the Command Center of Fun might refer to it as the Command Center of Pain.   Kayla has a bit of an anger management problem when it comes to playing with her dolls.   However, on the bright side of things there as been no causalities.   As you can see she is well defended and bunkered down pretty good.   We are still hoping for a peaceful diplomatic resolution, however, the diplomatic process is started to deteriorate.   We will keep you informed if the situation becomes worse.

It would appear that the little one is having fun with things.   We are doing well, and Kayla has started Daycare.   So far so good, things are going well.   She is still spoiled and not sleeping a lot by herself yet.   It seems she likes to be held or in the swing when she is sleeping.  We are trying to load up the newest picutres and stuff in the gallery.   I will try to keep everyone posted on things.   She has started making the cute baby noises from time to time.

We are so proud to share our baby Kayla with everyone.   She was born on Aug. 6th 2008 at 9:28 pm.   She was 18 inches long weighing in at 6.11 lbs.

Well, today someone that we all know was on The Today Show with Al Roker for his seventh-annual “Lend a Hand TODAY” series.   So, just like the title says, Where is Waldo?  If you look closely you should see someone that you know.   Don’t worry, if you “read more” of the aritcle you can see a better picture of Waldo.  What!?  You thought I would just let you see the other picture without tring to spot the person first!!

This year will be hard to beat because of our special gift.   We intended to do smaller gifts this year and focus more on family and friends and enjoying the time together.   I know … I know …. so what was the special gift already?   Well since you asked so nice, Laura and I have been blessed to have our first child.   Of coarse, that means our parents get to be Grandparents.   This is a picture that was taken after everyone opened our special little gift.   Everyone got a pin that said something to the effect of Expectant Grandma/Grandpa.   The picture didn’t quite get everyone into frame, but I wasn’t all that worried about it when I was taking the picture.