It's something I'd like to avoid, just because it's duplication. If there's a workaround, great. If I have to open and read a config file each time for each set of tests, then that's that.

You can put the duplicated code in a module (as you would in non-test code). Then your test scripts can look like:

use Test::More;
use MyApp::Frob;
use MyApp::Test::Config;

my $cfg = MyApp::Test::Config->cfg;
my $frob = MyApp::Frob->new($cfg->whoToFrob, $cfg->whatToFrob);
ok($frob, "can create a frob");
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