#!/usr/bin/perl

use strict;
#use warnings;

for my $regexp (
  qr/^((a*)b|a*b?d)*c\2$/,
  qr/^(a*b?d|(a*)b)*c\2$/,

  qr/^((a*)b|a*b?d())*c\2$/, # NOTE these two fixed to work the way
  qr/^(?|a*b?d()|(a*)b)*c\1$/, # I think they should work
  )
  {
  for my $string (qw( aabadcaa aababdcaa ))
    {
    print "\n$string\n$regexp\n";
    print $string =~ /$regexp/ ? 'Yes' : 'No', "\n";
    }
  }

print <<END;

This is perl 5, version 38, subversion 0 (v5.38.0) built for x86_64-linux-thread-multi

END