Unfortunately, callers(1) gives me the same result like current_comp->parent. With value of 0 I get the current_comp, so this doesn't help at all.

No one else an idea? Am I out of luck? Unfortunately the #mason on opn seems to be quite dead (it's empty after all) so I think I'll have to bug the mailing lists. Thanks anway for the try.
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use signature; signature(" So long\nAlfie");