Also changing the first capture to non-greedy should not affect the number of results (regexp is anchored on both sides), yet it does (for z? case, things work OK without it):

perl -e '"01234" =~ /^(.+?)(.+)((?:.z?)+)$(?{ print "$1 $2 $3\n" })(*F
+AIL)/'
0 123 4
0 12 34
0 1 234
01 23 4
[download]

It looks like a bug. It smells like a bug. It ate my whole project. But... Is it a bug?