I have strange problems inserting data in a MySQL (3.23.36) table. In a apparently casual way, my data are truncated. Here the code I'm using:

sub insert_msg
{
    my $author = $query->param('author');
    my $subject = $query->param('subject');
    my $body = $query->param('body');
    my $parent = $query->param('parent');

    my $thread;
    if ( $parent ) {
        my $sth = $dbh->prepare(qq|select id, thread from messaggi whe
+re id=?|);
        $sth->execute( $parent ) || die $DBI::errstr;
        my $hr = $sth->fetchrow_hashref();
        
        $thread = ($hr->{'thread'} == 0) ? $hr->{'id'} : $hr->{'thread
+'};
    }
    else {
        $thread = 0;
    }

    $body = validate( $body );
    
    $body = HTML::Entities::encode( $body );
    $body =~ s/\[(.*?)\|(.*?)\]/target($1, $2)/eg;
    $body =~ s/\[(.*?)\]/target($1)/eg;
    
    my $sth = $dbh->prepare( qq|insert into messaggi values(null, ?, n
+ull, ?, ?, ?, null)| );
    $sth->execute( $thread, $author, $subject, $body ) || die $DBI::er
+rstr;

    $template->process( $config->{'template'}->{'insert'} );
}
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Here the table's description:

CREATE TABLE `messaggi` (
  `id` int(10) unsigned NOT NULL auto_increment,
  `thread` int(10) unsigned default NULL,
  `data` timestamp(14) NOT NULL,
  `author` varchar(100) default NULL,
  `subject` varchar(200) default NULL,
  `body` text,
  `category` int(10) unsigned default NULL,
  PRIMARY KEY  (`id`),
  FULLTEXT KEY `body` (`body`),
) TYPE=MyISAM
[download]

As you can guess, it's a mysql-based webforum. Very simple.
First of all, I fetch information about the thread where the message has to be inserted. Then, I validate the $body using HTML::Parser, stripping HTML tags that are not valid. Then, I replace links with appropriate HTML, like in PerlMonks. Eventually, I insert the message in the database.

Sometime the $body is truncated, casually, apparently. For example, inserting the same message after some minute, the body is inserted correctly.

Thank you for every advice.