Perl
Contents
Beginning programming in Perl
- Introduction to Perl
- Beginning Perl -- PDFs of chapters of Beginning Perl.
- Perl.org Tutorials
Perl Documentation
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).
