my %d;
while (<DATA>) {
  my ($file, $line, $comment) = /^([^:]+):(\d+)\s+(.*)/
    or warn("unknown line, skipping: $_"), next;
  push @{$d{$file}{$line}}, $comment;
}

use Template;
Template->new->process(\<<'EOT', { d => \%d, env => \%ENV })
[%# USE Dumper; Dumper.dump(d); -%]
[%-
  FOREACH filek = d.keys.sort;
    filev = d.$filek;
    FOREACH linek = filev.keys.nsort;
      linev = filev.$linek;
      "<dt>$filek</dt><dd><b> line $linek</b>\n";
      FOREACH comment = linev;
        "  <ul>\n" IF loop.first;
        "    <li>"; comment | html; "</li>\n";
        "  </ul>\n" IF loop.last;
      END;
      "</dd>\n";
    END;
  END;
-%]
EOT
  or die Template->error;
__END__
comment_tmpl.tt2:1 This would be more readable if I turned on Template's space-stripping options.
comment_reader.pl:31 More informative error message would probably be good.
comment_reader.pl:71 Need a better explanation of data structure.
annotate.el:1 Should properly be in a mode...
annotate.el:11 Should be configurable variable
annotate.el:13 Formatting should be configurable in variable
annotate.el:11 Should automatically make "annotations" visible if it isn't already
annotate.el:21 Control-c keys are supposed to be for mode-specifics...