@array = ("x y.g z 123", "a b.f c 456", "d b.c w 321")

##</code><code>##

@include = ("b","q")

##</code><code>##


my %testHash = map { $_,1} @include;

foreach my $tmp (@array){
        my @tokens = split /\s+/,$tmp;
     	my ($test,$rubbish) = split /\./, $tokens[1];
	push (@keep, $tmp) if (exists $testHash{$test});
}