#!/usr/bin/perl -w

use strict;

my $input = "(abdc)(adc-b)";

my @expr;
while ($input =~ s!\(([-a-z,]+)\)!!) {
	my @items = split '', $1;
	my (@and, @or) = ();
	while (@items) {
		my $elem = shift @items;
		if ($elem eq '-') {
			push @or, shift @items;
		} else {
			push @and, $elem;
		}
	}
	push @expr, [ \@and, \@or ];
}

my $first = shift @expr;
my @output = @{ @$first[0] };
while (my $next = shift @expr) {
	my (%keep, %drop);
	@keep{@{ @$next[0] }} = ();
	@drop{@{ @$next[1] }} = ();
	foreach (@output) {
		next if (exists $keep{$_});
		$_ = undef if (exists $drop{$_});
	}
}

my $output = join('', grep{ defined($_) } @output);
print "Result is; $output\n";