Sorry for creating the confusion here, the _tagChar is the subroutine written by me only
and it looks like this

sub _tagChar
{
        my $self = shift;
        my ($tag, $data) = @_;
        return unless(defined($tag) && defined($data));
        vverbose(9,"Tag: ($tag), Data: ($data)");
        $self->xml->startTag("$tag");
        $self->xml->characters($data);
        $self->xml->endTag("$tag");
}
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and the characters sub of XML::Writer looks like this

 my $characters = sub {
    my $data = $_[0];
    if ($data =~ /[\&\<\>]/) {
      $data =~ s/\&/\&amp\;/g;
      $data =~ s/\</\&lt\;/g;
      $data =~ s/\>/\&gt\;/g;
    }
    &{$escapeEncoding}($data);
    $output->print($data);
    $hasData = 1;
  };
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but the question here is again when I take the data in a variabled the
value doesnt get replaced and if I pass the hardcode value it gets replaced
i.e. application/pdf
Please help and advise again.