# $logfilename being defined previously....
  my (%errors);
  open(LOGFILE, $logfilename) or die(qq{Can't open $logfilename for input: $!\n});
    while (my $line = <LOGFILE>) {
      # example format: mon day time server program[pid]: message
      my @lineparts = split(/\s+/, $line, 6);
      if ($lineparts[5] =~ m/^Error:/) {
        $errors{$lineparts[5]}{count}++;
        push(@{$errors{$lineparts[5]}{linenumber}}, $.);
      }
    }
  close(LOGFILE);

##</code><code>##

  print qq{ERROR REPORT\n\n}, 
    qq{Error message\tOccurrances\n\tLines found on\n\n};
  foreach my $k (sort keys %errors) {
    print $k, qq{\t}, $errors{$k}{count}, qq{\n}, 
      qq{\t}, join(q{,}, @{$errors{$k}{linenumber}}), qq{\n};
  }

##</code><code>##

ERROR REPORT

Error message   Occurrances
        Lines found on

Error msg 1     1
        13
Error msg 8675309       5
        3,7,21,55,82