in reply to Having a problem with negative look behind assertion
I would say only Athanasius has a correct answer yet, I see mistakes in the other answers. So I made sure and tested. This should work (and still uses only one regex):
if( $line =~ /^(?!fee).*[Bb]ar.*\.java/ )
This is a negative look-ahead fixed at the start of the line (with ^).
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Seekers of Perl Wisdom