Regarding requests for suggestions to improve your code's robustness...

My guess is that you are probably not using the strictures, since $config_file is not declared with my (at least, not in your sub):

use warnings;
use strict;
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When accessing an environment variable, it is a good practice to test if it is defined. If it is not defined, you could either die (as shown below), or assign it a default value:

my $config_file = (defined $ENV{'CONFPATH'}) ? 
                  $ENV{'CONFPATH'} :
                  die "Error: CONFPATH not defined.\n";
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Should <CFILE> really be <CONFFILE>?

It is also a good practice to close a filehandle when you are done.

These tips probably do not solve your specific problem, but hopefully they are small steps toward more robust code.