Your next step is to inspect what is in %CONFIG_FILE when you encounter that condition.

Use the following code:

       if ($file =~ /$key/) {
           $mapattach = $value;
           use Data::Dumper;
           print Dumper \%CONFIG_FILE;
        }
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Also output whenever you get a match on /$key/:

       if ($file =~ /$key/) {
           $mapattach = $value;
           use Data::Dumper;
           print Dumper \%CONFIG_FILE;
           print "'$file' matches /$key/, setting value '$value'\n";
        }
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Maybe there are two keys in %CONFIG_FILE that match the filename and the second one overwrites the first match in some cases? You are aware that hash keys are not ordered in Perl?