Synopsis
This is an error in the way the REXX script is written. There is a THEN keyword without some expression after it.
Cause
You tried to name a variable then in a place where the THEN keyword is illegal.
Cure
In certain instructions, you cannot use the (unquoted) REXX keyword THEN for a variable name.
Cause
You put a THEN keyword, but wanted no particular action taken so you left it blank after the THEN.
Cure
You should use the NOP keyword if you want no particular action taken.