mhh, good points.
I resorted to using eval since there seems to be no other way to "evaluate" a
process substitution inside a variable. This is possible with (e) for many
substitutions, but not for process subst.
I would be very interessted to hear if there are better way's to do this. Maybe
I too will ask around a bit on #zsh.

As for documentation: sure no problem
As for testing: I did extensive testing, but not on grml.

anyway, looking forward to the new release :-)
Getting back to you on this issue, if I can improve the function.