Heat oil in a large skillet. Add mustard seeds. As soon as they stop sputtering, add urad dal and cook for 1 minute until they turn golden brown.
Add red chile and curry leaves. After a few seconds, add carrot, beans and green chiles.
Add water and salt. Cook on medium heat for about 8 minutes, until vegetables are fork tender, stirring occasionally. All the water should have evaporated.
Add coconut and stir to combine.
Notes
Poriyal can be made with any variety of vegetables.