Difference between revisions of "Perl"
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=== Strings === | === 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: | ||
| + | |||
| + | <source lang="perl"> | ||
| + | my $foo = "Kim"; | ||
| + | print "Hi, $foo!"; # prints «Hi, Kim!» | ||
| + | </source> | ||
| + | |||
| + | But if the variable name is ambiguous, you can use {} characters to set it apart like so: | ||
<source lang="perl">$string = "${foo}worthy"</source> | <source lang="perl">$string = "${foo}worthy"</source> | ||
| + | And this way it won't get confused with another variable like <tt>$foow</tt>, or <tt>$fooworth</tt>, or what have you. | ||
| + | |||
| + | ==== Clarifying complicated string constructions using <tt>printf()</tt> or <tt>sprintf()</tt> ==== | ||
| + | |||
| + | When you're trying to build up a complex string by assembling many different variables and bits of text, things can quickly get unreadable: | ||
| + | |||
| + | <source lang="perl"> | ||
| + | my $msg = "At " . DateTime->now() . ", " . $user->name . " did $action" . | ||
| + | ", which made " . $action->object . " become " . $action->result . "."; | ||
| + | </source> | ||
| + | |||
| + | The Perl function <tt>[http://perldoc.perl.org/functions/sprintf.html sprintf()]</tt> 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, <tt>%s</tt> means "insert a string here". Then list the variables you want inserted. | ||
| + | |||
| + | So, the above example could be reformatted like this: | ||
| + | |||
| + | <source lang="perl"> | ||
| + | my $msg = sprintf("At %s, %s did %s, which made %s become %s.", | ||
| + | DateTime->now(), $user->name, $action, $action->object, $action->result); | ||
| + | </source> | ||
| + | |||
| + | <tt>[http://perldoc.perl.org/functions/printf.html printf()]</tt> works the same as <tt>sprintf()</tt>, except it immediately prints the string you built -- so, <tt>printf(''blah'')</tt> is pretty much the same as <tt>print sprintf(''blah'')</tt>. | ||
[[Category: Development]] | [[Category: Development]] | ||
Revision as of 03:03, 6 April 2013
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).
