my $protein = 'NOV';
my @keywords = (qw(novice niveau november paramonov nov supernova), "he said 'nov'");
print "Left-matches  /$protein/: $_\n" for grep { $_ =~ /\b$protein/i } @keywords;
print "Right-matches /$protein/: $_\n" for grep { $_ =~ /$protein\b/i } @keywords;
print "Contains      /$protein/: $_\n" for grep { $_ =~ /$protein/i } @keywords;
print "Contains      /$protein/ as word: $_\n" for grep { $_ =~ /\b$protein\b/i } @keywords;