This module provides a simple way to extend the Math::Symbolic parser with 
arbitrary functions that return any valid Math::Symbolic tree. The return 
value of the function call is inserted into the complete parse tree at the 
point at which the function call is parsed. Familiarity with the 
Math::Symbolic module will be assumed throughout the documentation.

This module is not object oriented. It does not export anything. You 
should not call any subroutines directly nor should you modify any class 
data directly. The complete interface is the call to use 
Math::SymbolicX::ParserExtensionFactory and its arguments. The reason for 
the long module name is that you should not have to call it multiple times 
in your code because it modifies the parser for good. It is intended to be 
a pain to type. :-)

The aim of the module is to allow for hooks into the parser without 
modifying the parser yourself because that requires rather in-depth 
knowledge of the module code. By specifying key => value pairs of function 
names and function implementations (code references) as arguments to the 
use() call of the module, this module extends the parser that is stored in 
the $Math::Symbolic::Parser variable with the specified functions and 
whenever "yourfunction(any argument string not containing an unescaped \) 
)" occurs in the code, the subroutine reference is called with the 
argument string as argument.

The subroutine is expected to return any Math::Symbolic tree. That means, 
as of version 0.133, a Math::Symbolic::Operator, a 
Math::Symbolic::Variable, or a Math::Symbolic::Constant object. The 
returned object will be incorporated into the Math::Symbolic tree that 
results from the parse at the exact position at which the custom function 
call was parsed.

Please note that the usage of this module will be quite slow at compile 
time because it has to regenerate the complete Math::Symbolic parser the 
first time you use this module in your code. The run time performance 
penalty should be low, however.

WWW: http://search.cpan.org/dist/Math-SymbolicX-ParserExtensionFactory/