"...AoA[oA[oA]...]]...iterate over the leaves...quit the iteration at an arbitrary point"

Perhaps Data::Rmap does the job?

use strict;
use warnings;
use Data::Rmap qw(rmap);

my @data =  [ [0], 1, 2, [ 3, 4, 5 ], 6, [ 7, 8, [ 9, 10 ], [ 11, [12]
+, 13 ], ], 14 ];

my $something = 5;

eval {
    rmap { $_ <= $something ? print : die; } @data;
};

__END__
monks>rmap.pl
0
1
2
3
4
5
[download]

Edit: Forgot to copy&paste something ;-) ...and fixed some entities

Best regards, Karl