How to insert certificate serial number and ssl verify result to http header both ?

Just as a general note, if you want to store more than one thing in the session table, you would first need to build a list containing each thing. Then store the list in the session table.

In your example, you could do this:

lset my_ssl_stuff {[SSL::cert 0] [X509::verify_cert_error_string [SSL::verify_result]]}
session add ssl [SSL::sessionid] $my_ssl_stuff 180

Then when you extract the value from the session table you would use the command "lindex" to extract the appropriate portion. Ie:

set my_ssl_stuff [session lookup ssl [SSL::sessionid]]
set ssl_cert [lindex $my_ssl_stuff 0]
set ssl_errstr [lindex $my_ssl_stuff 1]