$root_default: initial;
$root_implicit: initial;
$root_explicit: initial !global;

@mixin set_variable_inner() {
  $root_implicit: inner;
  $root_explicit: inner !global;
  $root_default: inner !default;
  $local_implicit: inner;
  $local_explicit: inner !global;
  $local_default: inner !default;
}

@mixin set_variable_outer() {
  $root_implicit: outer;
  $root_explicit: outer !global;
  $root_default: outer !default;
  $local_implicit: outer;
  $local_explicit: outer !global;
  $local_default: outer !default;
  @include set_variable_inner();
}

@include set_variable_outer();

result {
  root_default: $root_default;
  root_implicit: $root_implicit;
  root_explicit: $root_explicit;
  @if variable-exists(local_default) {
    local_default: $local_default;
  }
  @if variable-exists(local_implicit) {
    local_implicit: $local_implicit;
  }
  @if variable-exists(local_explicit) {
    local_explicit: $local_explicit;
  }
}