I'm working on parsing a large XML file of a blog backup and reordering and reformatting the text to be used in InDesign. The XML file is formatted somewhat like this:

...
<entry>
  <type>Post</type>
  <url>URL</url>
  <title>The title</title>
  <content>The blog post goes here</content>
</entry>
<entry>
  <type>Comment</type>
  <in-reference-to>URL</in-reference-to>
  <title>The title of the comment</title>
  <content>The content itself</content>
</entry>
...
[download]

Right now I have my code go through the XML file once, find all the comments, and put them in a temporary file using File::Temp. Here it is in pseudo code

my $tmpComments = File::Temp->new(SUFFIX=>'.txt') or die "File::Temp: 
+$!\n";
foreach (#Go through the whole xml file) {
  if ($type eq 'Comment') {
  # Parse the xml and save the parts as variables
  print $tmpComments "$posturl~~~$date~~~$author~~~$content\n";
  # $posturl holds the <in-reference-to> url
  }
}
[download]

I then loop through the xml file again to find and print out all the actual blog posts. On each pass I search the entire temporary file for any comments that start with the post url and add those comments to the post, like so (again in pseudo code):

foreach (#Loop through the xml file again) {
  print "$title\n";
  print "$content\n";
  ...
 
  seek $tmpComments, 0, 0 or die "Seek $tmpComments failed: $!\n"; #Re
+wind temporary comments file
  while (my $line = <$tmpComments>) {
    # Split each line, store url as $commentID
    my @process_comment = split(/~~~/, $line);
    my $commentID = $process_comment[0];

    # If the urls match, add it to the comments variable
    if ($commentID eq $posturl) {
      my $commentDate = $process_comment[1];
      my $commentAuthor = $process_comment[2];
      my $commentBody = $process_comment[3];
      $comments.= "$commentDate | $commentAuthor | $commentBody";
    }
  }
  print $comments;
}
[download]

It works just fine, but it takes forever with longer xml files, probably since it's uselessly looping through the temporary file so many times.

Is there a more efficient way of doing this?

Is there a way to use a cache to store all the comments indexed by the URL so that when I loop through the blog posts I can look at the cache and pull out the appropriate comments?

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