@a = qw( food bar baz );
$" = "\0"; 
print "Found\n" if index "@a", qq/foo/;     # Wrongly succeeds.
print "Found\n" if index "@a", qq/foo$"/;   # Rightly fails.
print "Found\n" if index "@a", qq/$"bar$"/; # Rightly succeeds...
print "Found\n" if index "@a", qq/$"baz$"/; # Wrongly fails.