I got this error HTTP::Message content must be bytes when running my program (it uses WWW::Mechanize). Here is the code:

    my $query = qq{
        
        <root><post_form_data_action object_name="$object->{reference_
+name}" object_id="$object->{reference_id}" object_version="1" form_na
+me="Bookmark" form_context="create" process_id="$object->{process_id}
+" > 
        <post_attribute_data attribute_name="SocialMediaAccount" >$acc
+ount</post_attribute_data> 
        <post_attribute_data attribute_name="Url" >$object->{url}</pos
+t_attribute_data> 
        <post_attribute_data attribute_name="Title" >$object->{title}<
+/post_attribute_data> 
        <post_attribute_data attribute_name="Content" >$object->{conte
+nt}</post_attribute_data> 
        <post_attribute_data attribute_name="Tags" >$object->{tags}</p
+ost_attribute_data> 
        <post_attribute_data attribute_name="Status" >$object->{status
+}</post_attribute_data> 
        <post_attribute_data attribute_name="Category" ></post_attribu
+te_data> 
        </post_form_data_action> 
        </root>
    };
    
    $mech->post( $CONFIG{BASE_URL} . "/synnd/webif.awr?undefined", Con
+tent => $query );
[download]

This error occurs only on few results but it's very weird. I look into $query and it's looks like containig only ASCII. I save $query value to the file with:

        open my $error, ">", "error.txt" or die $!;
        print $error $query;
        close $error;
[download]

Here is $query which produce the error:

        <root><post_form_data_action object_name="Buzz" object_id="-23
+789858" object_version="1" form_name="Bookmark" form_context="create"
+ process_id="92381" > 
        <post_attribute_data attribute_name="SocialMediaAccount" >Soci
+alMediaAccount:1592361</post_attribute_data> 
        <post_attribute_data attribute_name="Url" >http://myselfdevelo
+pment.net/index.php/2007/05/09/how-to-blow-your-mind-the-10th-dimensi
+on/</post_attribute_data> 
        <post_attribute_data attribute_name="Title" >How To Blow Your 
+Mind: The 10th Dimension   SAVE </post_attribute_data> 
        <post_attribute_data attribute_name="Content" >Ok.. the first 
+time I viewed this, I thought this would be easy… from the 1st dimens
+ion to the 2nd and so on… my brain fried around the 5th and sixth dim
+ension… never mind the 10th dimension.</post_attribute_data> 
        <post_attribute_data attribute_name="Tags" >science,video,phys
+ics,dimensions,mathematics</post_attribute_data> 
        <post_attribute_data attribute_name="Status" >New</post_attrib
+ute_data> 
        <post_attribute_data attribute_name="Category" ></post_attribu
+te_data> 
        </post_form_data_action> 
        </root>
[download]

What's wrong with my data? How i can fix this error?