Anybody else care to try?

Using 5.6.0 on Win32, I get repeated

Deep recursion on subroutine "main::A" at ack.pl line 11.
Deep recursion on subroutine "main::A" at ack.pl line 13.
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Looking at your code, I distrust what you are doing to save stack space.

Update: Yup. Add   print "A($_[0],$_[1])\n"; to the top of the function to watch it run off the rails. This is not a correct implementation of the Ackerman function.