For information about Perl's grep command, use perldoc -f grep.

To reverse the condition, negate the condition: grep { !( expression ) } LIST (Using a block is easier in many cases, and read perlop to find out when you can leave out the parens).
To reverse grep's output, use reverse: reverse grep BLOCK LIST or reverse grep EXPR, LIST

Lbh ebgngrq guvf grkg naq abj lbh pna ernq vg. Fb jung? :)   -- Whreq
[download]