sub R1{
    $_=sub{join"\0",split//,pop};"\0".&$_|&$_
}

##</code><code>##

sub R2{
    sub _{join"\0",split//,pop}"\0".&_|&_
}

##</code><code>##

sub R3{
    sub _{join$",split//,pop}$".&_|&_
}