If I'm on any computer that I can't get my IDE on, I use Vim as well. Here's a handy little bit of code for one's .vimrc file that allows for folding/unfolding of Perl subs:
if getline(v:lnum) =~ '^\s*sub\s'
elseif getline(v:lnum) =~ '\}\s*$'
let my_perlnum = v:lnum
let my_perlmax = line("$")
let my_perlnum = my_perlnum + 1
if my_perlnum > my_perlmax
let my_perldata = getline(my_perlnum)
if my_perldata =~ '^\s*\(\#.*\)\?$'
" do nothing
elseif my_perldata =~ '^\s*sub\s'
Here's a screenshot of what things look like if the above code snip is added into the config file (all subs are folded by default when opening a Perl file).
I keep a copy of my most basic vim config file in my Github for easy retrieval while I'm on systems I don't have control over.
Update: While in Vim's normal mode, zo will open/expand the folded sub, and zc will close it again.