Difference between revisions of "Perl"

Latest revision as of 04:08, 23 April 2013

Beginning programming in Perl

• Introduction to Perl
• Beginning Perl -- PDFs of chapters of Beginning Perl.
• Perl.org Tutorials

Perl Documentation

• Manual Pages
• Module documentation
• FAQ
• Too, a linux or Mac OS X machine with Perl installed will almost always have the perldoc tool installed...so if you like, you can also access all of the above information from the command line:
  • perldoc perl will give you a list of all the main perldoc pages
  • perldoc Module::Name gives you documentation for that module
  • perldoc -f function shows the documentation for that function
  • perldoc -q search-term searches the Perl FAQ for the term given
  • and of course perldoc perldoc tells you more about how to use perldoc =)

Commonly referenced perldoc pages

• perlsyn - Perl syntax
• perlop - Perl operators
• perlfunc - Perl functions
• perlvar - Perl special variables
• perlreref - Perl-style regular expression reference
• perlmodlib - The Perl Standard Module Library

Regular Expressions

Perl programmers tend to make extensive use of regular expressions, but they are also used in many other tools (eg vim, less, grep).

• Jeremy Friedl's book Mastering Regular Expressions is an excellent primer.

Perl Tips

Strings

Interpolating variables inside text

Most of the time, you can simply place a variable inside a double-quoted string, and Perl will expand it for you in the way you want:

my $foo = "Kim";
print "Hi, $foo!";     # prints «Hi, Kim!»

But if the variable name is ambiguous, you can use {} characters to set it apart like so:

$string = "${foo}worthy"

And this way it won't get confused with another variable like $foow, or $fooworth, or what have you.

Clarifying complicated string constructions using printf() or sprintf()

When you're trying to build up a complex string by assembling many different variables and bits of text, things can quickly get unreadable:

my $msg = "At " . DateTime->now() . ", " . $user->name . " did $action" . 
    ", which made " . $action->object . " become " . $action->result . ".";

The Perl function sprintf() lets you build up strings using a kind of mini-templating language. You specify the literal text you want first, with markers that indicate where you want to insert a variable. For instance, %s means "insert a string here". Then list the variables you want inserted.

So, the above example could be reformatted like this:

my $msg = sprintf("At %s, %s did %s, which made %s become %s.", 
    DateTime->now(), $user->name, $action, $action->object, $action->result);

printf() works the same as sprintf(), except it immediately prints the string you built -- so, printf(blah) is pretty much the same as print sprintf(blah).