Well, I've started dabbling in Tcl. It's something I've been meaning to do for Quite Some Time Now.
I have to say that the experience, over all, has been very satisfactory and non-frustrating. That is, it has not been what I expected it to be!
The Scary Thing About Tcl, as Perl hackers are typically led to believe, is its Obnoxious Shell-like Whitespace-based Parsage. Also its Ubiquitous Symbolic References. And "Variable Scoping is Hacked and Twisted, so Use Global Variables For Your Mental Health".
But in practice, I find that Tcl has an elegant -- if imperfect -- consistency that is easy to program in. Yes, it's been a mental adjustment, but not a huge one.
One of the things I like about Tcl is its Lispiness. Essentially, square braces are eval'ed like lists in Lisp, and curly braces are like quoted lists. A block of code is just a block of terms that might (might!) get sent to the eval function. In fact, Tcl's syntax is extremely reminiscent of Lisp's. (One thing that's different is Tcl's (less than desirable) sensitivity to newlines.)
I also like Tcl's built-in support for event loops.
Basically what it boils down to is that all the things I've heard people say to try to scare me away from Tcl have turned out to be bogus.
That's not to say there aren't a few good reasons to continue using Perl... but mostly they're cultural, or community things. The one thing about perl that can be said to be qualitatively better, as a language, is that it is possible to write things much more tersely. Well, I'm sure there are others. I'm sure the Tcl regex engine hasn't kept up with Perl's, for example.