use warnings;
use strict;
use Acme::Tools qw(intersect);

my @FILES = ("ABC","DEF","GHI","JKL","MNO","PQR","STU");

if (intersect(\@FILES, [qw(ABC GHI MNO)]) == 3) {
    print "yes\n";
}
else {
    print "no\n";
}

__END__

yes