un-determined behavior of asyncs

[Chaos Eternal]

hi gurus,

I wrote a short code to inspect the behavior of asyncs,
and find that neither the running time nor the order of execution is determined,
in fact , i find that the execution order of asyncs are random.

I just want to understand whether this random execution order of
asyncs is designed or desired or not-specified ?

thanks, the code is attached, the output follows:

$ guile async.scm
t2
((13700 1136293857 1) (18024 1136289128 0) (11235 1136295519 4) (11375
1136295012 3) (11444 1136294540 2) (8011 1136297645 9) (7978
1136297254 8) (7932 1136296817 7) (7735 1136296394 6) (3380 1136295978
5))
t1
((4262 1136289128 0) (317 1136293857 1) (221 1136294540 2) (199
1136295012 3) (228 1136295519 4) (215 1136295978 5) (203 1136296394 6)
(183 1136296817 7) (191 1136297254 8) (214 1136297645 9))

async.scm
Description: Binary data