$ perl t1.pl
1..4
ok 1 - mytest1
    1..2
    not ok 1 - sub1-test1
    #   Failed test 'sub1-test1'
    #   at /Users/ken/tmp/pm_subtest_mod/TMod.pm line 11.
    ok 2 - sub1-test2
    # Looks like you failed 1 test of 2.
not ok 2 - tmod
#   Failed test 'tmod'
#   at t1.pl line 11.
not ok 3 - mytest3
#   Failed test 'mytest3'
#   at t1.pl line 12.
ok 4 - mytest4
# Looks like you failed 2 tests of 4.