Are you sure the snippet you provide is the actual code giving the problem? Here an excerpt from XML::Simple:

    if($StrictMode  and  $dirn eq 'in') {
      croak "No value specified for 'ForceArray' option in call to XML
+$dirn()";
    }
    $opt->{forcearray} = 0;
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And $StrictMode is true only if you use XML::Simple in this way: use XML::Simple qw(:strict);

Another issue is in the file-reading part:

open(FILE, "someFile.DTD") or die "can't open file: $!";
#...
my $config = XMLin($FILE, forcearray => 1);
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This use of FILE and $FILE isn't going to work.