It may be important for you to make the distinction between version numbers of individual modules and of the entire program. Let your source control deal with the former with something like the following, assuming you're using CVS:

$My::Package::VERSION = substr(q$Revision$, 10);
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(There are lots of variations on this, just use one that works for you.)

For the latter, I'd actually recommend against what Corion mentioned -- mixing letters and numbers is a no-no for automatic version comparisons and will cause you lots of pain when dealing with CPAN. And even if you're never dealing with CPAN you might want to use some the tools that it uses to manage your own code.

My rules of thumb are:

• Don't go to version 1.0 until you have a fairly stable API
• Use hundredths as increments rather than tenths (too coarse) or thousandths (too granular). So you'd have 0.01, 0.02, 0.03... instead of 0.1, 0.2, 0.3... or 0.001, 0.002, 0.0003... This allows you to make incremental improvements while still leaving room for substantial updates (e.g., 0.41 -> 0.50).
• Incremental (+.01) updates should have roughly the same amount of change, if possible. This lets people get a feel for how often they need/want to upgrade.

Good luck

Chris
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