use strict;
my $str = ':smile_1:
:smile_2:
:smile_3:
:smile_4:
:smile_5:
:smile_6:
:smile_7:
:smile_8:
:smile_9:
:smile_10:
:smile_11:
:smile_12:
:smile_100:';
my $regex = qr/:smile_([0-9]{0,2}):/p;
my $subst = '<img src="/$1.png">';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html