use strict;
my $str = 'http://www.w3schools.com/jsref/jsref_regexp_exec.asp
https://translate.google.com/#en/pt/Thank%20you%20Engr!%20That%20is%20awesome.php
www.facebook.com/index.asp';
my $regex = qr/.*\.(\w{3,})$/mip;
my $subst = '$1';
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