Very interesting information, indeed. As I am sure many other monks before me and probably others after and in the future, I have tried a couple of years ago to rewrite in Perl a "my_map" and a "my_grep" functions (just for the sake of experimenting). And, if my memory serves me right, I ended up writing a simple anonymous function; then adding a code-ref prototype to my_map was all what was needed to mimic exactly the block syntax of map (getting rid of the sub keyword). So, I also considered the map block to be more or less equivalent to an anonymous function and I actually wrote today, just a few hours ago, in answer to another question of the original poster of this thread, that "the (map) block can be regarded as an anonymous function" (in this thread: map sub to list?). From the functional point of view that I was using, I think it is probably right to put it this way and that I probably don't need to change anything to my formulation, but it is quite interesting to know that from an implementation point of view, there is a significant difference which has an impact on performance. Anyway, thank you for the implementation details, this is very useful to know.