use strict;
use warnings;

use re 'eval';
#use re 'debug';

use Data::Dumper qw( Dumper );


my $amount = shift;

my @bills = (1, 5, 10, 20, 50, 100);


my $choices = join "\n   ",
              map { "(  .{$_} (?{ my \%r = \%{\$^R}; \$r{$_}++; +{ \%r } })  )*" }
              @bills;

my $regexp = qr/
   ^
   (?{ +{} })
   $choices
   $
   (?{ push(@matches, $^R) })
   (?!)
/x;


print($regexp, "\n");

our @matches;
('.' x $amount) =~ $regexp;
print(Dumper(\@matches));