...or, for a less subtle, more brute-force method: 
@words = qw (perl lerp lepp wombat);

$pattern = ".e..";
@pattern_elements = split "", $pattern;

word:
foreach $word (@words) {
    my @bag = qw (p r l); # Reset bag
    my @letters = split "", $word;
    
    print "\nTesting $word...\n";
    
    for my $i(0...$#letters) {    
        my $element = $pattern_elements[$i];
        
        # Create a character class with the letter bag
        my $class = '['.join ("", @bag).']';
        
        if ($letters[$i] =~ m/($class)/) {
            # If matched, remove the letter from the bag
            @bag = grep /[^$1]/, @bag; 
        } elsif ($letters[$i] eq $element) {
            next;
        } else {
            print "$word not matched\n";
            next word;
        }
    }
    print "$word matched!\n" if @bag == 0;
}

[download]
yields: 
Testing perl...
perl matched!

Testing lerp...
lerp matched!

Testing lepp...
lepp not matched

Testing wombat...
wombat not matched

[download]
Not sure how efficient it is, or even how robust it is, but heck, it looks like it does what you want. It tracks each letter in your search string against each character in a search pattern, makes a match (if possible) and shrinks the bag by the match. Hope this helps.

Gary Blackburn
Trained Killer

In reply to Re: Self-Shrinking Character Classes by Trimbach
in thread Self-Shrinking Character Classes by athomason

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