Below is sample code on how to lookup using the new technique.
proc fcmp outlib=work.funcs.test; subroutine s(a, b $, c $); outargs a, b; declare dictionary d; if c = 'add' then do; d[a] = b; d[b] = a; end; else if c = 'get_a' then do; a = d[b]; end; else if c = 'get_b' then do; b = d[a]; end; endsub; run; options cmplib=work.funcs; data _null_; a = 1; b='xxx'; call s(a, b, 'add'); call missing(a); put "Note: get_a before " a= b=; call s(a, b, 'get_a'); put "Note: get_a after " a= b=; call missing(b); put "Note: get_b before " a= b=; call s(a, b, 'get_b'); put "Note: get_b after " a= b=; run; Output: Note: get_a before a=. b=xxx Note: get_a after a=1 b=xxx Note: get_b before a=1 b= Note: get_b after a=1 b=xxx