OK - So I understand the issue now with PLIST, basically I would need to add
MVI? ?0(R3),C' '
after line 253. This makes sure that the proper end of the token is found even is some preexisting junk is there in the target ARGVARGS.
But I have no chance of seeing if the same problem exists in EPLIST let alone fixing it (for a start I could not test it!).
Therefore the safest thing to do is instead clear this
ARGVARGS DS CL257
down to zeros (or spaces?) first. The trouble is my S/370 is crap (nonexistent!), is this the most efficient/elegant way?
MVI? ARGVARGS,X'0'? ? ? ? ? ? ? ? ?* Zero start
MVC? ARGVARGS+1(256),ARGVARGS? ? ? * Propagate to the rest?
Anyway I will see it it works!