use strict;
use warnings;

BEGIN {
	package MyVars;
	use Exporter::Shiny;
	use B::Hooks::EndOfScope;
	
	sub import {
		no strict "refs";
		my $caller = caller;
		my $old_value = ${"$caller\::pi"};
		*{"$caller\::pi"} = do { my $new_value = 3.14159; \$new_value };
		on_scope_end {
			*{"$caller\::pi"} = \$old_value;
		}
	}
};

use Data::Dumper;

{
	use MyVars;
	BEGIN { print Dumper($pi) }
}

BEGIN { print Dumper($pi) }