list of letters or pattern: :otrwreh
master_letter_freq:
$VAR1 = {
          'w' => 1,
          'h' => 1,
          't' => 1,
          'o' => 1,
          'r' => 2,
          'e' => 1
        };
list of letters or pattern: ---w
thew
trow
list of letters or pattern:

##</code><code>##

list of letters or pattern: :otrwreh
list of letters or pattern: ---w
thew
trow
whew  ## this is the problem!! "w" is not allowed to repeat!
list of letters or pattern: exit

##</code><code>##

RESULT: foreach (@result)
        {
            my %seen;
            $seen{$_}++ for (split //,lc $_);
            
            foreach (keys %seen)
            {
                next RESULT if ($seen{$_} > $master_letter_freq{$_});
            }
        
            print "$_\n";
        }

##</code><code>##

foreach (@result)
{
    my %seen;
    $seen{$_}++ for (split //,lc $_);

    my $no_print = 0;
    foreach (keys %seen)
    {
        $no_print++ if ($seen{$_} > $master_letter_freq{$_});
    }

    print "$_\n" unless $no_print;
}