```sass
@use "sass:selector"
@mixin if-root-is($selector)
$current-sequences: & //.p .c
$result: ()
@each $sequence in $current-sequences
// [.p, .c]
$current: nth($sequence, -1) // .c
$root: nth($sequence, 1) // .p
$unify-root: selector.unify($root, $selector) // .p.x
$result: append($unify-root, $current)

@at-root #{$result}
@content


.p
.c
color: red
@include if-root-is('.p12')
color: green


```