I'm a bit more care-free with the forbidden knowledge than nobull, so I'll give you an example. Note, this doesn't pass strict. That should be a big red flag, but here it is:

{
    package a;
    our $foo = 1;
}
{
    package b;
    my $otherpkg = "a";
    my $varname = "$otherpkg\::foo";

    print ${ $varname }, "\n";
    
    # can be simplified as:
    print $$varname, "\n";

    # or the temp variable can be avoided:
    print ${ "$otherpkg\::foo" }, "\n";
}
[download]

Another solution would be to create an accessor sub in the package, and eliminate the package variable altogether.

use strict;
{
    package a;
    my $foo = 1;
    sub foo { $foo }
}
{
    package b;
    my $otherpkg = "a";
    print $otherpkg->foo, "\n";
}
[download]