MathML::Entities a content conversion filter for named XHTML+MathML 
entities. There are over two thousand named entities in the XHTML+MathML 
DTD. All the Entities defined in the XHTML+MathML DTD except the five 
"safe" ones (<, >, &, ", '), will be converted to the 
equivalent numeric character references or to utf-8 characters. Named 
entities which are not in the XHTML+MathML DTD are escaped. This makes the 
resulting XHTML (or XHTML+MathML) safe for consumption by non-validating 
XML parsers.

Unlike, HTML::Entities, the mapping between MathML named entities and 
codepoints is many-to-one. Therefore, there's no particular sense in 
having an inverse function, which takes codepoints to named entities.

Based on: HTML::Entities by Koichi Taniguchi <taniguchi@livedoor.jp>

WWW: http://search.cpan.org/dist/MathML-Entities/