Suggestion for EXECON.

[Snorre]

Hello JohnP,

I think your assumption about EXECON not doing symbolic calculation, i.e. not firing up the CAS, is right. You could do it by yourself:
EXECON("CAS(\"&1-&2\")",l1,l2)
or -- easier to enter --
EXECON("CAS(""&1-&2"")",l1,l2)

It seems that EXECON is just repeatedly doing an EXPR(...) on the string after substituting each &n-pattern by the corresponding list's element. So you could put nearly arbitrary content (e.g. whole program chunks) into the pattern. For example, you could print out what's going on:
EXECON("LOCAL x; IFERR x:=EXPR(""&1-&2""); THEN x:=""Nah!""; END; PRINT(""&1-&2 → ""+x); x",l1,l2);

Greetings