Stack Machine Interaction using forth

I am trying to solve a puzzle, The only pieces of information we were given were

( a b c d e — a^b^e )

I have a menu to interact with the stack using forth

& : ( a b — a&b )

| : ( a b — a|b )

^ : ( a b — a^b )

* : ( a b — a*b )

+ : ( a b — a+b )

– : ( a b — a-b )

apropos : search for functions

bneg : ( a — ~a )

choice : ( a b true — a ) ( a b false — b )

dup : ( a — a a )

flag : return "The secret flag"

pop : ( a — )

rot : ( a b c — b c a )

-rot : ( a b c — c a b )

swap : ( a b — b a )

How is a b c d e — a^b^e achieved?

What do the double hyphens signify? How is ( a b c d e — a^b^e ) achieved?