Package Mod; my $callback; sub set_callback { $callback = shift; } sub do_something { do_this(); do_that(); &$callback; do_something_else(); } . . . 1; __END__ #!/usr/bin/perl use strict; use warnings; use Mod; Mod::set_callback(\&print_rubbish); Mod::do_something(); sub print_rubbish ( print "Rubbish!\n"; }