# untested snippet
my @good_lines,@bad_lines;
foreach my $file_name (@file){
    open(MYFILE, $file_name)
      or die qq(Cannot open '$file_name' : $!\n);
    # Read file line by line
    my $line;
    while (defined $line = <MYFILE>) {
      # Does the current line match our RE?
      if ($line =~ /NOT|INVALID|MUST|ERROR/) {
        push @bad_lines, $line; # store it in @bad_lines
      } else {
        push @good_lines, $line; # store it in @good_lines
      };
    };
};

print "good: @good_lines";
print "bad : @bad_lines";