I tried to use ECB when I was a complete Emacs n00b, and I don't think I had enough basic Emacs skills to learn new things easily at that time, at least not complicated things like ECB.
When I finally managed to install it I don't think I ever managed to get the Perl stuff working properly (I used it for C++ at that time). Semantic doesn't support Perl IIRC, but ctags should work.
I also looked at it later to see if I could get PerlySense to hook into it, but again the elisp was way too magical for me at that time, having only put stuff in my .emacs file up until then. (I've basically learned elisp as I went along writing PS).
Maybe I should take a look at it again.
I put an improved regex-tool into PS, but it turns out I rarely use it
The Emacs perl debugger is brilliant, and I use it sometimes (but it needs to be Project aware, so a wrapper will go into PS eventually).
flymake to check syntax and Perl::Critic, but that's also wrapped and improved slightly in PS.
yasnippet, mostly for very simple but awkward-to-type things like unpacking sub/method parameter lists. I have special key bindings for extremely common things like "$self->", "->" "=>", and a curly block.
Home grown functions to reformat and align parameter lists for when they get too long.
Version control stuff, also streamlined into PerlySense (might not really be on-topic, but still useful)