Perl doesn't have real private package subroutines. However, it's possible to create a reference to an anonymous sub. Such a reference can be put in a scalar, and a scalar can be lexically scoped using `my'.
Most people don't use this, for several reasons. Some people don't like to have to use a sigil and a derefence operator every time they call the private sub, some people just don't like the idea.
When you look around in some modules, you'll see a lot of subs beginning with an underscore. Those subs are pretty much always meant to be private. If someone nevertheless decides to call it, that's his/her problem :)

I've never found a good reason for having really private subroutines. The underscore indicates it's something special, so the coder who uses it, knows he does so on his own risk.

A quote from perlmod:
Variables beginning with underscore used to be forced into package main, but we decided it was more useful for package writers to be able to use leading underscore to indicate private variables and method names. $_ is still global though. See also "Technical Note on the Syntax of Variable Names" in perlvar. 

2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$

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In reply to Re: private subroutine in package? by Juerd
in thread private subroutine in package? by Anonymous Monk

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