cheat sheets.

pop - Returns the last element in the array and deletes that element.

push - Appends its argument to the end of the array.

shift - Returns the first element of the array, deletes that 
        element, and shifts all other elements down one 
        location to fill its empty spot.

unshift - Shifts all elements of the array up one, and places its 
        argument at the beginning of the array.

each - iterates through the array

to get a slice of an array 
  my_array[5..7]

to delete a slice in an array
  my_array[2,2] = ["foo","bar"]

to replace foo and bar with tic, tac, toe
  my_array[2,2] = ["tic","tac","toe"]