I don't think you can use placeholders for table names.
The problem is that the resulting string will be quoted, as you see in that nice error message:
error in your SQL syntax near ''common_dict' WHERE word = 'aa''

What you can do is use prepare_cached() in the following way

foreach my $x (@checklists) {
    my $sth = $dbh->prepare_cached("SELECT word FROM $x WHERE word = ?
+");
    $sth->execute($word);
    my $ret = $sth->fetchrow_hashref();
    ...etc...
}
[download]

This way you won't get a performance hit for re-preparing the SQL statement every time.

--perlplexer