linear "push @tickets, $ticket" is wrong, here is an example:
12 has 1 children: 13
12 has 2 parents: 10 and 3
3 has 2 children: 5 and 12

to get all related tickets of 12, let's see how @tickets change in old way:

(10,3) # initial
(10,3,12) # after searching ticket 10
(10,3,12,5) # after searching ticket 3
(10,3,12,5,13) # after searching ticket 12

aparently, 5(child of 3) should appear right after 3 insetad of 12,
while 13(children of 12) should appear right after 12