% cat xxx.pl
    package script;

    $env = 1;
    $ENV = 2;

    print "\$env = '$env'\n";
    print "\$ENV = '$ENV'\n";
    print "\$script::env = '$script::env'\n";
    print "\$script::ENV = '$script::ENV'\n";
    % perl xxx.pl
    $env = '1'
    $ENV = '2'
    $script::env = '1'
    $script::ENV = ''
    %