Parenthesis text capturing (Perl RegEx)

Question

I'm back with a follow-up to this question. Let's assume I have the text

====Example 1====
Some text that I want to get that
may include line breaks
or special ~!@#$%^&*() characters

====Example 2====
Some more text that I don't want to get.

and use $output = ($text =~ ====Example 1====\s*(.*?)\s*====); to try and get everything from "====Example 1====" to the four equal signs right before "Example 2".

Based on what I've seen on this site, regexpal.com, and by running it myself, Perl finds and matches the text, but $output remains null or is assigned "1". I'm pretty sure that I'm doing something wrong with the capturing parenthesis, but I can't figure out what. Any help would be appreciated. My full code is:

$text = "====Example 1====\n
Some text that I want to get this text\n
may include line breaks\n
or special ~!@#$%^&*() characters\n
\n
====Example 2====]\n
Some more filler text that I don't want to get.";
my ($output) = $text =~ /====Example 1====\s*(.*?)\s*====/;
die "un-defined" unless defined $output;
print $output;

my ($output) = $text =~ /====Example 1====\s*(.*?)\s*====/; – Michal Gasek Jan 28 '14 at 15:45 — Michal Gasek, Jan 28 '14 at 15:45

mpapec · Answer 1 · 2014-01-28T16:00:29.943

3

Try with parentheses to force list context, and use /s when matching so . can also match newlines,

my ($output) = $text =~ / /s;

edited Jan 28 '14 at 16:00

answered Jan 28 '14 at 15:45

mpapec

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Tried, but `$output` still remains null. – KingBob Jan 28 '14 at 15:57

score 1 · Accepted Answer · answered Jan 28 '14 at 16:03

Two things.

Apply the /s flag to the regex to let it know that the input to the regex might be multiple lines.
Switch your parenthesis to be around $output instead of around the ($text ~= regex);.

Example:

($output) = $text =~ /====Example\s1====\s*(.*?)\s*====/s;

For example, putting it into a script like:

#!/usr/bin/env perl

$text="
====Example 1====
Some text that I want to get that
may include line breaks
or special ~!@#$%^&*() characters

====Example 2====
Some more text that I don't want to get.
";

print "full text:","\n";
&hr;
print "$text","\n";
&hr;

($output) = $text =~ /====Example\s1====\s*(.*?)\s*====/s;
print "desired output of regex:","\n";
&hr;
print "$output","\n";
&hr;

sub hr {
        print "-" x 80, "\n";
}

Leaves you output like:

bash$ perl test.pl
--------------------------------------------------------------------------------
full text:
--------------------------------------------------------------------------------

====Example 1====
Some text that I want to get that
may include line breaks
or special ~!@#0^&*() characters

====Example 2====
Some more text that I don't want to get.

--------------------------------------------------------------------------------
desired output of regex:
--------------------------------------------------------------------------------
Some text that I want to get that
may include line breaks
or special ~!@#0^&*() characters
--------------------------------------------------------------------------------

Parenthesis text capturing (Perl RegEx)

2 Answers2