func Char.Rot13() {
    return Char(this.Order() + 13)
        when this is >= 'a' and <= 'm' or >= 'A' and <= 'M'
    return Char(this.Order() - 13)
        when this is >= 'n' and <= 'z' or >= 'N' and <= 'Z'
    return this
}

func String.Rot13() {
    var cs = []
    for c in this {
        cs.Add(c.Rot13())
    }
    String.Concat(values: cs)
}

"ABJURER nowhere".Rot13()