Append to list stored in table key

What will be the values new_val?

How will you use it?

Will these keys expire? (you do not have set timeout)

you may create one subtable per IP address and define one key per val...

table add -subtable ip-[IP::client_addr] $c_val 1 3600

foreach c_val [table keys -notouch -subtable ip-[IP::client_addr] ] {
    do what you want
}