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:

function GetPerlFold()
  if getline(v:lnum) =~ '^\s*sub\s'
    return ">1"
  elseif getline(v:lnum) =~ '\}\s*$'
    let my_perlnum = v:lnum
    let my_perlmax = line("$")
    while (1)
      let my_perlnum = my_perlnum + 1
      if my_perlnum > my_perlmax
        return "<1"
      endif
      let my_perldata = getline(my_perlnum)
      if my_perldata =~ '^\s*\(\#.*\)\?$'
        " do nothing
      elseif my_perldata =~ '^\s*sub\s'
        return "<1"
      else
        return "="
      endif
    endwhile
  else
    return "="
  endif
endfunction
setlocal foldexpr=GetPerlFold()
setlocal foldmethod=expr
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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.