to get a program to return EXPR("%{1,2,3,3,4%}") as the set [1,2,3,4]

[compsystems]

expr (lowercase) is a CAS command for CAS environment #cas ... #end

expr("%{1,2,3,3,4%}") returns
[1,2,3,4] (History) =(.
returns set[1,2,3,4] =) (entryline or textbook flag: off)

expr("%{ a, a, b, c, c, d, ee, ee, ee,f %}") returns
[a,b,c,d,ee,f] (History) =(
returns
set[a,b,c,d,ee,f] =) (entryline or textbook flag: off)

For [hp-prime team]
I think that the history should be conversed the prefix SET[], to differentiate it from arrays, lists, vectors , tables, etc

expr("%{ a, a, b, c, c, d, ee, ee, ee,f %}") → set[a,b,c,d,ee,f]