What you have is an array of arrays of hashes. You can not strip off the outer array, or else you'd be trying to stuff a bunch of array refs into a single scalar, and that won't fly.

What I think you want to do is simply iterate over the encompassing array and act on each inner aref one at a time:

my @numbers = collect(@test);

sub collect {

    my @test = @_;
    my @all;

    for my $more_rec (@test){
        for my $number (keys %{ $more_rec }){
            my $numbers = $more_rec->{$number};
            push @all, $numbers->{agenda};
        }
    }

    return @all;
}
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However, it's doubly difficult to really understand what you want, because your data examples do not jive with what was in your collect() function. In there, you're extracting an href ($numbers) from within another href ($more_rec), and then from within $numbers, you're extracting the value of the agenda key. None of that is shown in your example data. Also, your collect() has at least one issue. You extract $number from keys(), but then never proceed to use it.