#use wml::ossp area=pkg:lib subarea=var
The supported post-operations are length determination, case conversion, defaults, postive and negative alternatives, sub-strings, regular expression based substitutions, character translations, and padding. Additionally, a meta-construct plus arithmetic expressions for index and range calculations allow (even nested) iterations over array variable expansions (..[..${name[#+1]}..]..). The actual variable value lookup is performed through a callback function, so OSSP var can expand arbitrary values.
Hint: There is also an ISO C++ derivative of the OSSP var library, named libvarexp. It is based on a development version of OSSP var and hence does not provide exactly the same amount of functionality. But it provides an ISO C++ API and so can be of interest to you if you are programming in ISO C++ (where OSSP var's ISO C API might be too boring for you).