The code that breaks is code that doesn't expect a thrown error.
A lot of my code uses 'if' to check the result from those operations; I don't see why errno would be very interesting.
OTOH, Pike is robust enough so the error is caught on a higher level anyway, but I don't think I'm alone in having code that uses if to check on those.
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On a sidenote, I think Pike still really needs an exception handling syntax.