use strict;

my $change = 16;
my @coins = reverse sort qw(2 5);

my $q='1'x$change;

my $solution = join'',map{qr(((?:.{$_})+))} @coins;

$q = ~/^()$solution$/
  or die "Error in regex construction";
{
  # This should maybe be done via @-, but I'm lazy:
  no strict;
  print(length(${$_})/$_, '*', $_) for (1..4)
};