org 100h

Start:

        mov cl, [len]
        lea di, [string]
        mov al, [elem]
        repne scasb
        jne OutputLine
        mov [di-1],byte '!'
        jmp Start

OutputLine:
        mov ah,09h
        mov dx,string
        int 21h

Finish:
        mov ax, 0c08h
        int 21h
        ret

len     db 11
elem    db 'a$'
string  db 'abrakadabra$'