in reply to
How to convert grabled characters into their real value
More context would be helpful. Where is your input string coming from, and what do you mean by "real value"?
Text::Unidecode only aims to provide a rough ASCII transliteration of the underlying characters, and it is self-admittedly quite bad at Thai. Is this really what you want?
Update: also, if you don't know about it already, be sure to check out Encode, the core Perl module that deals with character encodings.
When's the last time you used duct tape on a duct? --Larry Wall