static bool set(const astring &variable_name, const astring &value);
//!< adds or creates "variable_name" in the environment.
/*!< changes the current set of environment variables by adding or
modifying the "variable_name". its new value will be "value". */
static bool set(const astring &variable_name, const astring &value);
//!< adds or creates "variable_name" in the environment.
/*!< changes the current set of environment variables by adding or
modifying the "variable_name". its new value will be "value". */