use strict;
use Math::Combinatorics;

my $firstLetter="c";
my $str="a?1,a?2,a%3,b?2,b?3,b%5,c%4,c%5,c?6,d%2";
my $substring = "a?,b%,c?";


my @combos = Math::Combinatorics::combine(4,split ",",$str);

foreach my $combo (@combos) {


	## check if numbers are all unique
	my $hash = {};
	my ($count) = grep { ++$hash->{$_} > 1 } map { (split '')[2] } @$combo;
	next if defined $count;


	## place $firstLetter with largest weight in first position
	
	
	## ensure that substring strings are contained within the combination

}