WOO HOO!

Yes, that did it.

Making my main script ignore $SIG{CHILD} and making the child ignore $SIG{INT} and $SIG{HUP} makes it work the way I want it to.

Your code snippet almost works out of the box. Just had to change:

$SIG{INT} = $SIG{HUP} = sub{} ;   # child
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To

$SIG{INT} = $SIG{HUP} = 'IGNORE';   # child
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Thanks!