foreach my $fn ( @file ) {
    open $fh, $fn or die $!;
    my $dont_process = 0;
    while ( my $line = <$fh> ) {
        $dont_process = 1;
        # regex from OP
        last if ( $line =~ m/(sudden|unexpected)?\s+death|(deceased|passed\s+away\s*|\s*died\s*|\s*dying)(?!death\s+benefits)/);
        $dont_process = 0;
    }
    close $fh;
    next if ($dont_process);
    # Process file here
}