src = 'x = --1\n"W" "Y" / "Z"'; p = stmt:match(src); x = (infix.to_prefix(p))
a = rosie.env.ast.from_parse_tree(x, rosie.env.common.source.new{text=src})
messages = {}
e.compiler.compile_block(a, e.env, nil, messages)
rplx = e:compile('x')

then:

    > rplx:match("WY")
    table: 0x7f9e81fa27e0	0	false	4	3
    > rplx:match("WZ")
    table: 0x7f9e81cab080	0	false	5	4
    > rplx:match("W")
    false	1	false	4	4
    >