reorder word in MIPS. keep first and last letter in same position

the task is to randomly change around the middle characters of a word but keep the first letter and the last letter in the same place. i'm new to mips and am finding this quite difficult. here's what i have so far, it rearranges the word whilst keeping the last letter intact but i dont know how to keep the first letter in the same place? any help would be much appreciated. thanks

.data

String: .asciiz "library\n" length: .word 7

.text 
.globl main

main: lw $t0, length

        jal print
        j exit

print: la $a0,String li $v0,4 syscall bgtz $t0, MoveString jr $ra

MoveString: lb $t1, String li $t2, 0 move $a1, $a0 lb $t3, length sub $t3, $t3, 2

MoveStringLoop:

                lb $t4, 1($a1)
                sb $t4, 0($a1)
                add $a1, $a1, 1
                add $t2, $t2, 1

                blt $t2, $t3, MoveStringLoop

             sb $t1, 0($a1)

            sub $t0, $t0, 1
            b print

exit: li $v0, 10 syscall