use strict;
my $str = 'source.com';
my $regex = qr@(http(s)?://)?(([a-zA-Z])([-\w]+\.)+([^\s\.]+[^\s]*)+[^,.\s])@p;
my $subst = '<a href="http$2://$4">$0</a>';
my $result = $str =~ s@$regex@$subst@r;
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