Try peg - it's a grep-like command line tool that has an option -z to show context. It's at:

http://cpan.mirrors.uk2.net/authors/id/A/AD/ADAVIES/peg-2.20

You supply an expression (typically a regexp) which will be true for the context lines you want. So to recursively search files beneath your cwd you'd run:

 peg yoursubname -z "/^\s*sub /"

Common context matching code can be stored in peg's user initialization files (see the docs for the details) and then called using a label. I use the single letters 'p' for Perl subroutine context and 'c' for C function/struct context. So in practise you would simply run:

 peg -z p yoursubname