modify stage question

[UCDI]

I would like to have a really basic extraction job that can accept either * (or whatever code/string/anything) OR a list (col1, col2, col3) to feed to a modify stage. The idea is that the user could either extract specific columns (KEEP #param#) or all the columns (KEEP *).

The trouble is that KEEP * does not work. Nor does KEEP (space).
Nor does Specification = "empty string" or "space" ...

I guess what I am asking is, can I tell a modify stage to DO NOTHING via some specification magic command?

I know I can work around this with annoying amounts of complexity. My best take on it so far is to default parameter to #drop bogus#, use a transformer to add the bogus column, and if the parameter is overwritten it must contain "keep col1, col2, .." ... this works but its clunky.

[ShaneMuir]

Parameterise the specification value and pass either your required keep statement or the phrase NOWARN

[UCDI]

That works, Thanks!!