Set the environment variable PERL5LIB or PERLLIB for all the scripts

export PERL5LIB=/path/to/lib

Adding a path to the beginning of @INC. Good for the specific script

   unshift @INC, '/path/to/lib';

The same but with the standard tool:

use lib '/path/to/lib';           # good for the specific script

On the command line. Good for this invocation only.

perl -I /path/to/lib
How to change @INC to find Perl modules in non-standard locations