Simple Coverage Analyzer

        package Devel::Coverage;

        sub DB::DB {
          my ($package, $file, $line) = caller();
          $files{$file} = 1;
          $covered{$file}[$line] = 1;
        }

        END {
          for my $file (keys %files) {
            my $array = \@{"::_<$file"};       
            my ($executable, $covered) = (0, 0);
            for my $line (1 .. $#$array) {
              next if $array->[$line] == 0;
              $executable += 1;
              $covered += $covered{$file}[$line];
            }
            printf STDERR "%4d/%4d (%3.0f%%) covered in %s.\n",
              $covered, $executable, 100*$covered/$executable, $file
                 unless $executable == 0;
          }
        }

In numeric context, @{"::_<foo"} elements are special
They are equal to zero only when the line is not executable

        10/  31 ( 32%) covered in /usr/local/lib/perl5/5.6.0/Exporter.pm.
        10/  70 ( 14%) covered in /usr/local/lib/perl5/5.6.0/Getopt/Std.pm.
         8/  12 ( 67%) covered in /tmp/Devel/Coverage.pm.
        60/  74 ( 81%) covered in ./MAKE_SLIDES.