Without getting into details, you can view "27 88" as a base-256 system (except that we don't use extra symbols for numbers greater than 9, but decimal representations). Having this in mind, you can calculate the port using
$calc((27 * 256) + 88) = $calc(27 * 256 + 88)
You can make an alias if you like:
alias calcport return $calc($replace($1,$chr(32),* 256 +))
$calcport(27 88) returns "7000".