Pseudocode of a function key supply

supply.raku

use Term::ReadKey;

sub function-keys(:$echo) {
    supply {
        my @seen;
        whenever key-pressed($!echo) -> \value {
            @seen.push: value;
            if @seen eqv [1,2,3,4] {
                emit associated function key value;
                @seen = ();
            } 
        }   
    }   
}