Example of letting refinements loose

loose-ref.red

Red []
system/lexer/pre-load: func [src][
    ws: charset reduce [space tab newline] 
    ws+: [some ws] 
    dig: charset "0123456789" 
    num: [some dig] 
    parse src [any [
        "myfunc" s: ws+ 2 [num ws+] 
        any [i: ["/r3" | "/r4"] ws+ num ws+ (
            move/part i s 3 
            s: skip s 3
        )] 
    |   skip]]
]
myfunc: func [one two /r3 three /r4 four][
    case/all [
        r3 [print ["three ->" three]] 
        r4 [print ["four ->" four]] 
        true [print ["args ->" one two]]
    ]
]
myfunc 1 2 /r3 3
;three -> 3
;args -> 1 2
myfunc 1 2 /r3 3 /r4 4
;three -> 3
;four -> 4
;args -> 1 2
myfunc 1 2
;args -> 1 2