in reply to XS/Inline::C and ellipsis syntax

Note: this is XS only; I don't know if Inline supports varargs method signatures

See "Variable-length Parameter Lists" in perlxs. You'll have to change the vatest method signature (but you'd have to do that anyway to make it XS compatible). Which may mean that foo() has to change the way it calls vatest.

Perl Contrarian & SQL fanboy