Good point about POSIX. My Perl servers usually have:
use POSIX ":sys_wait_h";
Yes, on some platforms, setting up the sigaction stuff to a NULL handler will cause an "auto reap", but AFAIK that is not universal - I'm thinking about the low level C calls that Perl would use. In this case, this is an issue of how the OS deals with sigaction() handlers, not how Perl itself works. Perl cannot do what C cannot do.
I guess where I'm at is that the code I suggested is going to work on all platforms all the time (AFIK). I agree that 'IGNORE' will work on almost all platforms. I'm just not sure about the difference between "almost all" and "all". This detail probably doesn't matter for this app - it doesn't sound like a "general purpose" application as far as the OP is concerned.
So YMMV. Setting "IGNORE" is not "wrong" and it is "easier".
We both agree on the main issue here:
that the right way to deal with this is to explicitly do something with the CHLD signal: either a) explicitly ignore it which hopefully will cause the OS to "autoreap" the child or b)set a simple subroutine like I suggested. As long as one of these options "works", then it will work in all cases of child death: a) if the child kills itself (maybe a via a die statement) or b)I kill my own child or c)somebody else kills it.