clients have specifically expressed a concern about the ability to maintain our/their Web apps written in Perl should my business go bust
That is -of course- a legitimate concern. However it is not perl-specific. If your system would work with PHP, the concern would be the same.
Possibilities to address this concern would be
- show that perl is a mainstream-language, nothing exotic (e.g use the Tiobe Index)
- show that there are thousands of capable perl-programmers around ... not only PHP-coders
- show that your system/code is well-documented, so anyone can take over
- prove that your system is as stable as others (after all you are in business for 10 years)
So the programming-language you use should not be the biggest issue. However (as CountZero
wrote) you will still face the
competition of the open-source CMS systems...