V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

RCL
       Runtime Control Library


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

RCL

   Reduced Control Language.  A simplified job control language
   for OS360, translated to IBM JCL.  "Reduced Control Language
   for Non- Professional Users", K. Appel in Command Languages,
   C. Unger ed, N-H 1973.