How to parse a string according to the grammar from user input in MIPS.

Here is some of my code for user input but I need it to parse the user input.

.data

buffer: .space 20

str1: .asciiz "Enter in the problem: "

str2: .asciiz "You wrote: "

.text

main:

la $a0, str1 # Load and print string asking for string

li $v0, 4

syscall

li $v0, 8 # take in input

la $a0, buffer # load byte space into address

li $a1, 20 # allot the byte space for string

move $t0, $a0 # save string to t0

syscall

la $a0, str2 # load and print "you wrote" string

li $v0, 4

syscall

la $a0, buffer # reload byte space to primary address

move $a0, $t0 # primary address = t0 address (load pointer)

li $v0, 4 # print string

syscall

li $v0, 10 # end program

syscall