Hmmm, a few fixes so you can have 0 counts for some of the coins.

use strict;

my $change = 16;
my @coins = sort { $b <=> $a } qw(2 5);

my $q='1'x$change;

my $solution = join "", map { qr[((?:.{$_})*)] } @coins;

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