On Wed, 21 Sep 2011, Wolfgang Schuster wrote:
> Am 21.09.2011 um 05:20 schrieb Aditya Mahajan:
>
>> The following works in MkIV but fails in MkIV:
>>
>> \unprotect
>> \def\!!yesandon{yes,on}
>> \doifinsetelse{yes}\!!yesandon
>
> \ExpandSecondAfter\doifinsetelse{yes}\!!yesandon
>
> It¢s awkward but this how it works in MkII.

\ExpandSecondAfter is MkII only, so I cannot use it for code that is to be 
used in both MkII and MkIV. So, I re-request my original proposal:

in core-gen.mkii

  \def\p!doifinsetelse#1#2#3#4%
    {\donefalse
     \edef\!!stringa{#3}%
     \ifx\!!stringa\empty
     \else
-     \processcommalist[#4]\p!docheckiteminset
+     \processcommacommand[#4]\p!docheckiteminset
     \fi
     \ifdone\expandafter#1\else\expandafter#2\fi}


Aditya