|XP is just a number|
The complexities of writing a CMS make it a daunting task, even for the experienced programmers. But, as pointed out in the above replies, there is more to CMS than Perl, or coding of any kind.
First, there is the architecture. How will the system work, what resources can be used, who will design the database?
Secondly, there is interface design. I have clients who have paid big bucks for exotic CMS's, but who shun them because of their complexity and difficulty in actual use.
Thirdly, there are security issues--even well-meaning users can unwittingly input crazy stuff.
Lastly (well, not really), there's the coding and testing itself.
IMHO, check out off-the-shelf systems, or open source ones like Typo3. Are you sure you even need a database-driven CMS? Look at editors like Macromedias Contribute.
Take it from one who is there, learning Perl smartly enough to write a workable and safe CMS will be a long process. "Order out" is my advice.
"A little yeast leavens the whole dough."