sub offby {
        my($dist,$word,@possibles)=@_;
        my($re)=sprintf(
                q|^%s:%s$|,
                join(q|.?|,map{q|(\w*)|}(0..$dist)),
                join(q|.?|,map{"\\".($_+1)}(0..$dist))
        );
        my(@suggestions);
        #print "user $word regexp $re\n";
        foreach(@possibles) {
                my($str)="$word:$_";
                if($str=~/$re/) {
                        push(@suggestions,$_);
                }
        }
        return(@suggestions)
}