Nope. I even tried replacing USR1 with something available on Windows (a couple of somethings, actually: TERM, INT, NUM17 (just for grins)), but to no avail.

t\001_basic.t .....
1..63
# start on_start
ok 1 - not working max
ok 2 - called by manager
# end   on_start
ok 3 - called by child
# start on_start
ok 4 - not working max
ok 5 - called by manager
# end   on_start
# start on_working_max
ok 6 - working max
ok 7 - called by manager
# end   on_working_max
# start on_enqueue
ok 8 - called by child
ok 9 - working max
ok 10 - called by manager
# end   on_start
# start on_working_max
ok 11 - working max
ok 12 - called by manager
# end   on_working_max
# start on_enqueue
ok 13 - working max
ok 14 - called by manager
# end   on_start
# start on_working_max
ok 15 - working max
ok 16 - called by manager
# end   on_working_max
# start on_enqueue
ok 17 - working max
ok 18 - called by manager
# end   on_start
# start on_working_max
ok 19 - working max
ok 20 - called by manager
# end   on_working_max
# start on_enqueue
ok 21 - working max
ok 22 - called by manager
# end   on_start
# exit_code: 1
# exit_code: 2
[download]

Hangs right there.