Added note on how to make perlcritic.vim work

INSTALL.md

 You could actually have your .vimrc symlink point right to local/mydots/...
 I find this more flexible, though.
 
+### perlcritic_vim ###
+
+Additionally, if you want to use perlcritic.vim, you need to:
+
+*   install Perl::Critic (from CPAN)
+
+*   put bin/perlcritic\_vim to your PATH
 
 Instructions for git
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