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

SNOBOL4

    A quite distinct descendant of SNOBOL, developed
   by Griswold et al in 1967.  SNOBOL4 is declarative with
   dynamic scope.  Patterns are first-class data objects that
   can be constructed by concatenation and alternation.  Success
   and failure are used for flow control.  Delayed
   (unevaluated) expressions can be used to implement
   recursion.  It has a table data type.  Strings generated at
   run time can be treated as programs and executed.

   See also vanilla.

   SNOBOL 4 (http://snobol4.org/).

   (ftp://apple.com/ArchiveVol1/Unix_lang).

   A FOLDOC parser in SNOBOL4
   (http://www.topcat.hypermart.net/foldoc.html)!

   ["The SNOBOL4 Programming Language", Ralph E. Griswold et al,
   P-H 1971].

   (2011-01-05)