How to convert grabled characters into their real value

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

My program is like this:

 use utf8;
  use Text::Unidecode;
  print unidecode("ต้มยำกุ้ง");
[download]

But the output is the same: ต้มยำกุ้ง This ต้มยำกุ้ง is a grabled character of thai word Tom Yum with Prawns.

Can anybody tell me exact way to do this?