use FindBin qw( $RealBin );

use lib "$RealBin/../lib";
[download]

is basically equivalent to

use Cwd            qw( abs_path );
use File::Basename qw( dirname );

use lib dirname(abs_path($0)) . "/../lib";
[download]

(I don't know if the latter works on VMS.)

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Note that you should always use $RealBin. Using $Bin will cause your program to break if it's run via a symlink.