Perl

opendir D, '.' or die "Could not open current dir: $!\n";
my @filelist = grep(/[A-Z]{2}_\w{2,5}/i, readdir D);
closedir D;

my @ar = ( "a", "b", "c");
print "found b in @ar\n"  if ( grep (/b/, @ar));
print "notfound d in @ar\n"  if ( grep (!/d/, @ar));