After parsing an HTML file with HTML::TreeBuilder one gets back a large nested data structure:

my $tree = HTML::TreeBuilder->new_from_file($filename);

In the interest of efficiency, I would like to develop Perl modules which have the HTML parsed and already in-memory at mod_perl startup time:

package html::page::hello_world;


my $tree = HTML::TreeBuilder->new_from_file('/html/hello_world.html');

sub new {
    $tree
}

1;

This way, the module is used at server startup time and the constructor call incurs no delay due to parsing the HTML file. However, there is one problem: once the returned tree is modified, the new would return that same modified tree instead of a tree representing a fresh parse of the HTML file.

I therefore want to clone the tree and return a clone:

package html::page::hello_world;


my $tree  = HTML::TreeBuilder->new_from_file('/html/hello_world.html');
my $clone = $tree->clone;

sub new {
    my $retval = $clone;
    $clone = $tree->clone;
    $retval;
}

1;

But I don't want the overhead of making the new clone in the same process. I want to do something like a fork and return the pre-made clone to the caller immediately so it doesn't have to wait and manufacture a new clone in a separate thread/process.

Could anyone recommend a strategy/module for doing this?

In reply to fast return of HTML::Tree object clones (via threads/forks)? by metaperl

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