I'm not sure how you backup the statement that Perl is declining, but anyway.

There's a huge difference between writing sysadmin tools and writing business oriented applications. (Unless your business is to provide sysadmin tools. ;-)

In my shop, the sysadmins are free to use almost any tools, languages, etc. to get their work done. OTOH, when it comes to business supporting applications, with end user interface, the situation is very different. This is when our middle level management starts to worry.

My personal experience is that Perl does have a very short and low learning curve when it comes to writing different 'tools' to be used by IT folks.

The learning curve may quickly become long and steep when you want to create a business oriented application, very often combining techniques like CGI, DBI (or SybPerl), using non standard libraries written as OO or not plus adding your own modules to cover your shop-specific topics. Especially if you want to create some shared business objects to be reused by other Perl applications. Add to this that the CGI application shall create JavaScript to help the user orient through the application, sometimes even JS that eval()'s more JS and it becomes tricky. (Did someone mention 'security' as well?)

Furthermore, there is (at least in Central Europe) a huge lack of good training. There are commercial training courses, but those that I've found around where I live are all beginners courses covering the first chapters in the llama. Which is good, but not enough.
Because after the introduction course, my colleagues ask me how to proceed. When I tell them to go on-line, read books and otherwise participate, they are unhappy. Yes, many of them still haven't really learnt how to take advantage of the 'Net. And yes again, not enough people (fewer and fewer?) appreciates to RTFM. They all want quick solutions. And no, they don't appreciate to spend their evenings reading the Cookbook or the Camel. (Some odd colleagues, I admit. ;-)

You can repeatedly have quick solutions using Perl, but that requires efforts to learn. And this learning stage (where I'm still at) is not quick if you need to do something big.

Too many people (around where I make my living) want quick solutions to everything with no or little investment.
(Do I sound old? Yeah, I guess I am. That's how you become after 20+ years in this business. ;-)

Conclusion: In my shop, the middle management are worried what will happen if I leave.
Questions like: "Who will take over all this Perl stuff?" and "How can we get a new colleague up to speed on this Perl thingy within a week or two?" are commonplace here. Which in a way creates a resistance.

I'd say: Momentum! When there is a hord of Perl programmers available the middle management will sleep well during the nights. (At least concerning "The Perl Problem". ;-)
I'm working very hard to create the momentum that is necessary in our shop and I hope you do the same. (Biker points a finger at the reader.)

"Livet är hårt" sa bonden.
"Grymt" sa grisen...