Joined: 07 Feb 2009 Posts: 1124 Location: Vilnius, Lithuania
I'd suggest you change your compile procedures in the test environment to actually use both compilers, and check both listings for error messages. V6.2 may very well output far more informational, warning and even error messages than V4.2.
Been there, done that, with the transition of OS PL/I V2.3.0 to Enterprise PL/I V3.5.0. Right now the transition to Enterprise PL/I V5.2.x gives even more messages pointing to questionable code.