our $var; # Declare a variable in the current package.
*var = \$main::var; # Create an alias in the current package to package main's $var;

##</code><code>##

package Foo;
our $var = 42;
print __PACKAGE__, ": $var\n";
print \$var, "\n";

package main;
*var = \$Foo::var;
print __PACKAGE__, ": $var\n";
print \$var, "\n";

##</code><code>##

Foo: 42
SCALAR(0x559ec7e7b6a0)
main: 42
SCALAR(0x559ec7e7b6a0)