History variables

Implemented as a class:

class HistoryVar(v) {

    has history = []
    has variable = v

    method ≔(value) {
        history << variable
        variable = value
    }

    method to_s {
        "#{variable}"
    }

    method AUTOLOAD(_, name, *args) {
        variable.(name)(args...)
    }
}

var foo = HistoryVar(0)

foo ≔ 1
foo ≔ 2
foo ≔ foo+3
foo ≔ 42

say "History: #{foo.history}"
say "Current value: #{foo}"

Output:

History: [0, 1, 2, 5]
Current value: 42