use 5.010;
use Scope::Upper qw(localize UP);
our $foo = 42;
sub foo {
  localize '$foo', 1, UP;
}
sub bar {
  say "start bar: ", $foo;
  foo();
  say "end bar: ", $foo;
}
say "before bar: ", $foo;
bar();
say "after bar: ", $foo;