RATIONALE: Drugs used in chemotherapy, such as cladribine and cytarabine, work in different ways to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. Imatinib mesylate may stop the growth of cancer cells by blocking some of the enzymes needed for cell growth. Giving cladribine and cytarabine together with imatinib mesylate may kill more cancer cells.