This is my first monkish reply, so hopefully everything is formatted correctly.

PASE (Portable Application Solutions Environment) is an integrated OS/400 runtime for porting selected *NIX applications. It works by making applications think they are running on AIX, which I take it, is the problem. You may be able to use an OS/400-specific QSHELL command to infer that you are running on an AS/400. QSHELL is a (somewhat) Korn shell environment on OS/400.

I can't check this now because I am in front of an AS/400 without Perl installed, but, I believe that the command interpreter for system and backtick will be the PASE QSHELL. If that is true, then you could try an OS/400-specific QSHELL command like those below:

===> STRQSH

> sysval QMODEL
   570

> sysval -n SYSNAME
   MYSYSTEM

> sysval QSRLNBR
   1234ZRM
[download]

I think that `sysval` is a valid AIX command, but I bet that `sysval QSRLNBR` is not.

Google qshell strqsh for iSeries QSHELL stuff

DSPSYSVAL documentation from IBM

--chase