If you receive the 2nd line-to-echo always right after the first line, you could use the "event" of receiving the first matching line to set some kind of "one time marker". Something like:
if (Twitter Update isin $strip($1-)) && (!%twitter.updated) {
echo #newbox $1-
set -eu5 %twitter.updated x
}
elseif (%twitter.updated) {
echo #newbox $1-
unset %twitter.updated
}
elseif (http://twitter.com/ScoobeeDoo isin $strip($1-)) { echo #newbox $1- }
Else I think we'd have to see a further part of the script in question - some on sockread I guess - to find a sollution.
Edit: Sorry, I just realized you receive this in a channel/query. I hope you got the idea and it's of use for you though
And nope, there is no such command. you'd have to "count" the remaining lines-to-relay yourself.