#!/usr/bin/perl -wl

    use strict;

    my @db = qw(aaa bbb ccc ddd eee fff);
    my @in = qw(aaa fff);
    my %h;

    # Initialise the hash using a slice
    @h{@in} = undef;

    print "@db";

    @db = grep {not exists $h{$_}} @db;

    print "@db";

    __END__

    Prints:

    aaa bbb ccc ddd eee fff
    bbb ccc ddd eee