Now the best result for PL/I is:
“The limit for OS PL/I on a z/OS machine with 4Gb seems to be A=15, the limit for Enterprise PL/I on the same machine seems to be A=23, and the limit for PL/I for Windows on a 16Gb system seems to be A=26.”
http://rosettacode.org/wiki/Man_or_boy_test#PL.2FI
However, the article in Russian “RSDN Magazine” #2, 2013 describes a new PL-program for Windows Vista 32 bit and A=27
http://www.rsdn.ru/article/pl1/PL1ex7/pl1ex7.xml
New program has direct control stack and uses array for recursion