in reply to Strange bevahiour of grep function.

Hard to read, but if you want to invert a logical clause you also have to switch and to or and invert all sub-clauses.

see De_Morgan's_laws

And consider to use List::MoreUtils 'any' instead of grep.

HTH =)

Cheers Rolf

( addicted to the Perl Programming Language)

update

s/ List::Util / List::MoreUtils /

In Section Seekers of Perl Wisdom