c:\@Work\Perl>perl -wMstrict -le
"my $c = q{asdfghjk};
 print qq{    original: '$c'};
 ;;
 my @regex = (
   { lh => q{(gh)}, rh => q{__$1__}, },
   { lh => q{(h_)}, rh => q{_h!$1!}, },
   );
 ;;
 for my $hr_s (@regex) {
   $c =~ s[ (?-x)$hr_s->{lh}]{ qq{qq{$hr_s->{rh}}} }xmsgee;
   print qq{intermediate: '$c'};
   }
 ;;
 print qq{       final: '$c'};
"
    original: 'asdfghjk'
intermediate: 'asdf__gh__jk'
intermediate: 'asdf__g_h!h_!_jk'
       final: 'asdf__g_h!h_!_jk'