But use won't work properly unless you do that, so it is a good tradition to follow.

In which sense?

#!/usr/bin/perl -l

use strict;
use warnings;

use lib sub {
    pop eq 'Foo.pm' &&
      do {
          my $mod = join "\n", (map <<".EOM", 'A'..'Z'), "1;\n";
# --------------------
package Foo::$_;

sub new {
    print __PACKAGE__;
    bless [], shift;
}
# --------------------
.EOM
          open my $fh, '<', \$mod or die $!;
          $fh;
      };
};

use Foo;

Foo::J->new;
Foo::A->new;
Foo::P->new;
Foo::H->new;

__END__
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