Apparently Template had some problems tracking nested
BLOCKs and so they made a change which broke a Jemplate test that was counting on the wrong behavior, so now Jemplate can't compile on Template 2.21_2 and up, latest stable being 2.22.
It was really fun to debug even though before this experience I didn't know Jemplate and Template too well. I just forked Jemplate on github, converted the bad test from Test::Base (which I don't understand much) to Test::More and changed the test to is_string from Test::LongString to really understand where the problem was.
There is a bug standing on this (which I couldn't add to because I didn't open it) and I've emailed Robert Krimen regarding it.
Open Source FTW!