Placing a block in procedures not working with Local Variables?

Hi, I was making a mod today, and I wanted to make a little custom cave generation script (just a test, it obviously can get a lot better than this).

I tried using this script and putting it on a test block on the "On click" event, but it doesn't seem to work. I've tried replacing the local variable fields with coordinates

and then it works (but I obviously can't run this without using custom variables, it was just a test for placing one block on itself).

The conclusion I got is that block placement doesn't support local variables (for some reason?) or that I just made some stupid mistake.

NOTE: the block with this procedure on doesn't spawn in any of the blocks requested, meaning that it stops at the first lines and the problem is located there.