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',
},