Well, yes, but that's only when you are doing something in pure C. If you now do something in pure C, and use XS for it, porting it to Perl6/Parrot would be reasonable straightforward. But a lot of XS code deals with Perl internals, whether that's pure XS or Inline::C.

especially knowing that Inline::C will be in the 5.10 core.

Right. 5.10. When will that happen? After more than a year, we still have no 5.9.0, or even goals for 5.9.0. I might be pessimistic, but I think any new Perl development going on that's going to be released "soon" will be found in 5.8.2 and 5.6.2/3. I had hoped the p5p BOF in Paris would shed some light on the timepath for 5.10, but there wasn't anything in the minutes, so I guess it wasn't discussed.

Abigail