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) =~ $regexp; print(Dumper(\@matches)); #### >perl 546453.pl 20 (?x-ism: ^ (?{ +{} }) ( .{1} (?{ my %r = %{$^R}; $r{1}++; +{ %r } }) )* ( .{5} (?{ my %r = %{$^R}; $r{5}++; +{ %r } }) )* ( .{10} (?{ my %r = %{$^R}; $r{10}++; +{ %r } }) )* ( .{20} (?{ my %r = %{$^R}; $r{20}++; +{ %r } }) )* ( .{50} (?{ my %r = %{$^R}; $r{50}++; +{ %r } }) )* ( .{100} (?{ my %r = %{$^R}; $r{100}++; +{ %r } }) )* $ (?{ push(@matches, $^R) }) (?!) ) $VAR1 = [ { '1' => '20' }, { '1' => '15', '5' => '1' }, { '1' => '10', '5' => '2' }, { '1' => '10', '10' => '1' }, { '1' => '5', '5' => '3' } ]; #### { '1' => '5', '5' => '2' '10' => '1' }, { '5' => '4' }, { '5' => '2' '10' => '1' }, { '10' => '2' }, { '20' => '1', },