Yup, you could do it with grep, by reversing the match. Match the restricted word against the input word:

my @restricted_words = qw ( 
  funk  
  shucks 
  crud
); 
if (grep $word =~ /$_/, @restricted_words) {
  print "wash your mouth out!\n";
} else {
  print "Such a nice boy\n";
}
[download]

That code will be very slow, however, because it's recompiling the regex each time. Although you could avoid that problem with qr//, it would be simpler to skip grep and just make one big regex:

my @restricted_words = qw (
  funk
  shucks
  crud
);
my $restricted_re = '(?:' . join('|', @restricted_words) . ')';
$restricted_re = qr/$restricted_re/;
if ($word =~ $restricted_re) {
  print "wash your mouth out!\n";
} else {
  print "Such a nice boy\n";
}
[download]

This approach will give you both speed and flexibility. Enjoy!