#!/usr/bin/perl -w
use strict;

print unindent(<<'END');
	test
		test2

END

print unindent(<<'END', "(?: {4}|\t)");
    test
		test2

END

print unindent(<<'END', '');
	I don't want this text
	to be unindented.
END

##</code><code>##

sub unindent
{
    my ( $data, $whitespace ) = @_;
    if ( ! defined $whitespace )
    {
        ( $whitespace ) = $data =~ /^(\s+)/;
    }
    $data =~ s/^$whitespace//mg;
    $data;
}