::: => {
    ~ '\g<0>'
    '\g<0>_'=> {
        /0_/ ::= '1'
        /01_/ ::= '10'
        /11_/ ::= '1_0'
        /^1_/ ::= '10'
    }
}

::: => {
    ~ '\g<0>'
    /[aei]/ ::= ~ 'aei'
    /[ou]/ ::= ~ 'ou'

    /[aeiou]/ ::= '_'
}