if (exists $DiagCodes{$_})
{
    printf $fh1 "    %s: %d, %d\n",
#        *** Change here: ^
                $DiagNames{ $DiagCodes{$_} },
                $_,
                $Diags{$key}->{$_};
}
else
{
    printf $fh1 "    Unrecognized code: %d\n", $_;
#                       *** Change here: ^
}