Finds the full path to a script’s bin directory, letting you use relative paths to that directory without needing to know the actual location:

use FindBin;
use lib "$FindBin::Bin/../lib";

or:

use FindBin qw($Bin);
use lib "$Bin/../lib";

FindBin exports the following variables:

If you invoke Perl with the -e option or read the Perl script from STDIN, then FindBin sets both $Bin and $RealBin to the current directory.