Says tilly:

a platform where kill is not implemented...

It may be interesting to note that there's no reason why kill 0 can't be implemented on any system, even one that doesn't support other uses of kill.

I wouldn't bother pointing this out, except that Chris Nandor added kill 0 support to MacPerl just a couple of weeks ago, for precisely this purpose.

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Mark Dominus
Perl Paraphernalia