While investigating a bug in WebGUI/AssetExportHtml.pm, I came across this code that splits an asset's URL into a path and filename. 

        my $url = $asset->get("url");
       # ...
        my $path;
        my $filename;
        if ($url =~ /\./) {
            $url =~ /^(.*)\/(.*)$/;
            $path = $1;
            $filename = $2;
            if ($filename eq "") {
                $filename = $path;
                $path = undef;
            }
        } else {
            $path = $url;
            $filename = $index;
        }

It seems to work alright except when an asset URL has a directory that contains a period, then $filename will contain a directory separator, causing a later call to mkpath() to not create the entire path, and causing FileHandle->new() to sometimes complain about trying to open a directory.

Here's a patch that fixes one problem but not another: Assets that have a URL that's a descendant of an asset with a URL with a . in it don't get created at all

Parent: My.Test.Asset <- created as a file
Child: My.Test.Asset/My.Test.Child <- Not created at all, no error .

I think the best way to solve this would be to have each exported asset be its own directory. Ugly for the file system, perhaps, but it would export a site that's functionally identical to the generated site (save for Apache possibly putting trailing / on everything).