Why is it that when the sigCHLD signal is ignored, system() always returns -1?

-------------------- prog1.pl ----------------- 

#!/usr/bin/perl
$SIG{'CHLD'} = 'IGNORE';
system('prog2.pl');
print "return value is ", $?>>8, "\n";

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-------------------- prog2.pl ------------------ 
#!/usr/bin/perl
exit 5;

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If $SIG{'CHLD'} = 'IGNORE' is commented out, the return value is 5, which is what I expect. If it is left in, the return value is -1.

Is ignoring sigCHLD not recommended when using system?

I tested this on Linux, FreeBSD and Solaris with two versions of perl, all with the same results, so I assume this is something that is not really a bug. I've just never run across this before, and am looking for some insight.

20031105 Edit by Corion: Added CODE tags

In reply to why does ignoring sigCHLD corrupt return value from system()? by fiberhalo

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