Returns the current value (in string form) of an environment variable with the given name
Implemented by: GWBASIC, bwbasic, bw32, QBasic, VBDOS
With variations:
Also written as:
MS QuickBASIC allows both an assignment of a new value to an environment variable and its retrieval. More over, the function may receive a number as argument, for returning the value of the Nth environment variable.