The Free On-line Dictionary of Computing (30 December 2018):

FX-87

   Effects.  A polymorphic language based on Scheme, allowing
   side effects and first-class functions.  It attempts to
   integrate functional and imperative programming.
   Expressions have types, side effects (e.g. reading, writing or
   allocating) and regions (stating where the effects may occur).

   Versions: FX-89, FX-90.

   (ftp://brokaw.lcs.mit.edu/).

   ["The FX-87 Reference Manual", D.K. Gifford
    et al, MIT/LCS/TR-407, Oct 1987].

   (1995-01-31)