use strict;
use warnings;

use myfirstaddin  ();
use mysecondaddin ();

if (defined $ARGV[0] && $ARGV[0] eq 'second'} {
   mysecondaddin->import('runonce');
} else {
   myfirstaddin->import('runonce');
}

print "hello world";
runonce();
myfirstaddin::runonce();
mysecondaddin::runonce();

##</code><code>##

# myfirstaddin.pm

package myfirstaddin;

BEGIN {
   require Exporter;
   our @ISA       = qw( Exporter );
   our @EXPORT_OK = qw( runonce  );
}

# Other "use" statements go here.

sub runonce { print "This is file myfirstaddin."; }

1;

##</code><code>##

# mysecondaddin.pm

package mysecondaddin;

BEGIN {
   require Exporter;
   our @ISA       = qw( Exporter );
   our @EXPORT_OK = qw( runonce  );
}

# Other "use" statements go here.

sub runonce { print "This is file mysecondaddin."; }

1;