For paths that are always relative to the script's location, the core module FindBin works well:

use FindBin;
require "$FindBin::Bin/routines.pl";
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Update: hippo makes a good point that require will search @INC, so yet another way to make it work is with lib, as I showed here, and below. But I also agree with Discipulus' point that turning the file into a separate package might be a good idea too.

use FindBin;
use lib $FindBin::Bin;
require "routines.pl";
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