run-once code

[David Storrs]

Given this code:
     
    if ( some_expensive_lookup_function() >= $MAX_RECORDS ) {
       mark_that_we_have_reached_max_records();       
       return;
    } 

After I enter that block once, I never want to evaluate the condition
again--I want the code to completely disappear from the bytecode (or,
at least, be jumped around).  How would I do that in Perl 6?

(I recall seeing something about how to make assertions drop out, but
I want to be able to do this at run-time, not compile-time.)

--Dks