my @items = ();
foreach my $subset ( keys %lookingFor )
{
    foreach my $item ( @$subset )
    {
        push @items, $item;
    }
}
my $rxMatchItems;
{
    local $" = q{|};
    $rxMatchItems = qr{(?:@items)};
}

##</code><code>##

while ( <$fh> )
{
    next unless m{$rxMatchItems};
    print $writeFh $_;
}