Re^3: STDERR going to string

[Anonymous Monk]

because re-opening STDERR decouples perl's STDERR from the called C library's STDERR

It will probably work if you save/dup STDERR and restore it

open my $errsave, '>&', STDERR
  or do { print "couldn't dup STDERR: $!"; exit 2; };
open STDERR ...
...
open STDERR, '>&', $errsave
  or do { print "couldn't restore/dup STDERR: $!"; exit 2; };