# export $MyPackage::var to $YourPackage::var
    *YourPackage::var = \$MyPackage::var;

##</code><code>##

    $callpackage = 'YourPackage;
    $pkg = 'MyPackage';
    $sym = 'var';
    ${"${callpkg}::$sym"} = \${"${pkg}::$sym"};

##</code><code>##

#!perl -l

{

    my $var = 7;
    *Foo::var = \$var;

    print $Foo::var;

    foo();

    print $var;

}

sub foo {
    # changes both $Foo::var and the lexical $var
    $Foo::var = 8;
}