use Test::AsyncSeq;

my $id  = Test::AsyncSeq->get_sequence_id;
my $id2 = Test::AsyncSeq->get_sequence_id( "frobnicate" );
    # would be "frobnicate1" or smth

# somewhere in threads/callbacks
is_after( $id, "start" );
# elsewhere

is_after( $id, "event2", "start" );

# more elsewhere
is_after( $id, "event3", "start" );

# finally
is_after( $id, "finish", "event2", "event3" );