$x = 'main';
Foo::talk();

package Bar;

$x = 'Bar';
Foo::talk();

package Foo;

sub talk {
    my ( $package, $filename, $line ) = caller;
    print "Calling package is '$package'\n";
    printf "Caller's \$x is: '%s'\n", ${ $package . '::x' };
}

__END__
Calling package is 'main'
Caller's $x is: 'main'
Calling package is 'Bar'
Caller's $x is: 'Bar'