Im not sure, and have not tested this, but my guess would that Case 3 would be the most effecient. According to perlop qw() "generates a real list at compile time". It seems to me that would be the most efficient way of doing things. Of course at this point in the docs they are comparing qw() to split(' ', $STRING) but it does lead me to believe the list is created once, and simply sticks arround somewhere. But I could be wrong, and often am. Just my two cents.