OK, took some finding but this might be the problem. The blank lines in your config file are creating a blank key entry in the %CONFIG_PARAMS hash i.e. "" => undef. When you loop through the keys at some point the match becomes

 if ($file =~ //) {
   $mapattach = undef;
 }
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Because the order is random it depend which keys follow as to whether it gets corrected. The fix is to add a line to skip the blanks lines in here

# parse the config file
while (<FILE>) {

  # remove leading spaces
  $_ =~ s/^\s+//g;

  # remove trailing spaces
  $_ =~ s/\s+$//g;

  # ignore comments
  next if $_ =~ /^#/;  

  # ignore blanks
  next unless /\S/;

  my @params = split /=/ , $_;

  $CONFIG_PARAMS{$params[0]}=$params[1];

}
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A better way would be use a regex to extract the key from the filename and match directly like this.

my $mapattach;
# add () inside // to capture match
if ($file !~ /($CONFIG_PARAMS->{'OUTCRIT'})/) {
  Println "Skipping $file, doesn't match $CONFIG_PARAMS->{'OUTCRIT'}";
  next OUTBOUND;
} else {
  $mapattach = $CONFIG_PARAMS->{$1};
}
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poj