constant::tiny - Perl pragma to declare constants


    use constant::tiny;
    use constant PI    => 4 * atan2(1, 1);
    use constant DEBUG => 0;

    print "Pi equals ", PI, "...\n" if DEBUG;


This module is a lightweight version of the Perl standard module Here are the keys differences:

  • only works on Perl 5.10+ in order to simplify a good part of the code

  • doesn't support Unicode names; please use the standard module if you need to create constants with Unicode names

  • stricter rules about valid names, only allow names with alphanums ([a-zA-Z0-9] and underscore (_), allowing one optional leading underscore

In order to simplify its usage, constant:tiny uses the normal constant API. The main advatange is that switching your code to constant::tiny means simply adding it before the first use constant. The disadvantage is that, obviously, both modules can't be used at the same time. If the normal constant was loaded before constant::tiny, the latter won't do anything, letting the normal constant do the work.

Other than this, the usage is (nearly) exactly the same as with the standard constant module. For more details, please read constant.


The original reason to write this module was that, starting with version 1.24, constant always loaded, which consumes some memory. Usually, this is not problematic, but in some particular cases (embedded Perl, frequently forked programs à la CGI), the increased memory cost can become a concern.

Therefore, this module was written as a alternative solution, with no support for Unicode names, so that programs working in memory constrained environments could have a better control.

Funnily enough, the day constant::tiny was released on CPAN (the code had been written two months earlier as a proof of concept), Brad Gilbert proposed a patch for constant in order to delay loading until necessary.

Therefore constant::tiny is less useful (which is good news), but can still address specific needs, if you want to restrict constant names to alphanums only.


You can find documentation for this module with the perldoc command.

    perldoc constant::tiny

You can also look for information at:


Please report any bugs or feature requests to contant-tiny at, or through the web interface at I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.


This module is heavily based on, originaly written by Tom Phoenix, Casey West, Nicholas Clark, Zefram and many other folks from the Perl 5 Porters.


Sébastien Aperghis-Tramoni <sebastien at>


This module is free software; you can redistribute it or modify it under the same terms as Perl itself.