I have checked all the DESCRIPTION of Net::SSLeay, even check the code of the IO::Socket::SSL, that module used the Net::SSLeay to make ssl connection. But I can not find any help.

The only clue is about set_info_callback function in Net::SSLeay. But the description is disillusionary:

"Sets the callback function, that can be used to obtain state information for $ssl during connection setup and use. When callback is 0 (NULL), the callback setting currently valid for ctx is used. ??? (does this function really work?)"

Net::SSLeay::set_info_callback($ssl, $cb);
 # $ssl - value corresponding to openssl's SSL structure
 # $cb - pointer to function ???
 #
 # returns: no return value
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And I have a try, it seem that function can not work well in perl.