Source : Free On-Line Dictionary of Computing

PPL
     
        Polymorphic Programming Language.  An interactive, extensible
        language, based on {APL}, from {Harvard University}.
     
        ["Some Features of PPL - A Polymorphic Programming Language",
        T.A. Standish, SIGPLAN Notices 4(8) (Aug 1969)].
     
        (1994-10-06)