Copyright 2009 Kevin Ryde This file is part of constant-defer. constant-defer is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. constant-defer is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with constant-defer. If not, see . constant::defer makes subroutines similar to the builtin constant.pm, but with the value calculation deferred until the sub is actually run. use constant::defer FOO => sub { calculate; return $something }; This is handy for big or slow things only needed sometimes, or where at least the pain can be put off the point needed. Lazy or deferred calculations can be hidden behind a scalar variable too. The choice between a sub and a variable is a matter of style or personal preference. Both ways have advantages, see the constant::defer POD for some notes. The constant-defer home page is http://user42.tuxfamily.org/constant-defer/index.html