# mod.pm
package mod;
sub load {
   print(<DATA>);
   print("loaded\n");
}
load();
1;
__DATA__
some data

##</code><code>##

# script.pl
BEGIN { print("Before 'use mod;'\n"); }
use mod;
BEGIN { print("After 'use mod;'\n"); }
use mod;

##</code><code>##

Before 'use mod;'
some data
loaded
After 'use mod;'