open(my $master_file, '<', "file1") or die "couldn't open master";
my %valid = map { chomp; ($_ => 1) } <$master_file>;
close $master_file;
open(my $data_file, '<', "file2") or die "couldn't open data file";
while (<$data_file>) {
	my ($key) = split /\s/;
	print if $valid{$key};
}
close $data_file;