I guess the problem with the special characters in the "tmpl_var".
The "special characters" are not might be the problem*. Based on my test, the reason you are not getting the expected result is because the template contains an error. Note the missing text, indicated below: 
<TMPL_VAR NAME=NEW_A/B/C>
          ^^^^^

[download]

When I changed the template as indicated above, it worked fine for me.

On an unrelated note, I would avoid assigning to %hash and simply do $template->param( 'NEW_A/B/C' => 3 );.

HTH

*Update: Softened wording based on esper's comment (thanks for mentioning it).

In reply to Re: How to Set the 'tmpl_var' value in HTML::Template by bobf
in thread How to Set the 'tmpl_var' value in HTML::Template by kulls

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