Ok,
I have tested with DBI and it works great.
Anyway, I have checked with the mysql command "show full processlist;" what is doing the server when it hangs on with Net::MySQL, and this is the result:

mysql> show full processlist;
+----+-------+-----------+--------+---------+------+-------+----------
+-------------+
| Id | User  | Host      | db     | Command | Time | State | Info     
+             |
+----+-------+-----------+--------+---------+------+-------+----------
+-------------+
| 56 | root  | localhost | NULL   | Query   |    0 | NULL  | show full
+ processlist | 
| 57 | mysql | localhost | Weblib | Sleep   |  137 |       | NULL     
+             | 
+----+-------+-----------+--------+---------+------+-------+----------
+-------------+
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Also, when running a "truss" command on UNIX, it says something similar:

send(4, 0x081B6F68, 46, 0)                      = 46
   *\0\0\003 S E L E C T   *   F R O M   U s e r s   W H E R E   C
   S L   =   ' h s a n c h e '
recvfrom(4, 0x081B70B0, 1460, 0, 0x08047530, 0x0804796C) = 144
  01\0\00102 ,\0\00203 d e f06 W e b l i b05 U s e r s05 U s e r s
  03 C S L03 C S L\f !\018\0\0\0FD\0\0\0\0\0 6\0\00303 d e f06 W e
   b l i b05 U s e r s05 U s e r s\b L a n g C o d e\b L a n g C o
   d e\f !\006\0\0\0FE\0\0\0\0\005\0\004FE\0\002\0\v\0\00507 h s a
   n c h e02 e s05\0\006FE\0\002\0
recvfrom(4, 0x081F7520, 1460, 0, 0x08047530, 0x0804796C) (sleeping...)
[download]

I don't know why is so lazy this process and want to sleep always! :)
So, I'm going to use the script with DBI
Thanks to you 2 for your advice, guys