Here's mine, from a discussion on OO in January 1996.

Notice that I used a totally different mechanism to prevent duplicate entries for one line.

sub input
  {
  while (<>) {
     # parse the line into words
     my %temp;
     while (/\b\w+\b/g) {
        ++$temp{$&};
        }
     # add the found words to my global results list
     my $key;
     while (($key)=each(%temp)) {
        push (@{$concord{$key}}, $.);
        }
     }
  }


sub output
  {
  my @words= sort keys %concord;
  my $key;
  foreach $key (@words) {
#     print "$key @{$concord{$key}}\n"
     print ("$key ", join (', ', @{$concord{$key}}), "\n");

     }
  }

input;
output;
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