# Exporter before use
package Module1;

require Exporter;
our  @ISA = qw(Exporter);
our @EXPORT = qw(&fn1 &fn2);

use Module2;
use Module3;

# use before Exporter
package Module1;

use Module2;
use Module3;

require Exporter;
our  @ISA = qw(Exporter);
our @EXPORT = qw(&fn1 &fn2);