$dictfile="/some/path/to/dictfile";
#Dictfile should have a all words (or regex for words), one per line
open (DICT, $dictfile) or die "Can't open $dictfile:$!";
while(<DICT>){
	$words{lc($_)}=1;  #using hash as cheap lookup
	#Note that a "real" dictionary file will nail you on efficency here.  Perhaps a Dbm would be better?
}
while(<>){
	foreach $word (split($_)){
		if (!defined($words{lc($word)})){
			print "$.:$word?\n";
		}
	}
}