Modifying a list you're using in a for loop is a really bad idea.

        foreach my $c ( @{$child_aref} ) {
                @{$child_aref} = grep { $_ ne $c } @{$child_aref} if (
+ waitpid($c, WNOHANG) < 0 );
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The help in perlsyn says this :-

If any part of LIST is an array, "foreach" will get very confused if y
+ou
add or remove elements within the loop body, for example with "splice"
+. So
don't do that.
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