How do i skip portions of a loop after getting my answer?

I am trying to make a loop that modifies a certain value in a matrix and skip to the end of the loop after the modification is made. Right now the value will be modified, but is modified again before the loop can end and I don't know how to fix it.

     world = ['#' '.' '.' '.' '.' '.' '#' '.' 'v' '#'
              '.' '#' '.' '#' '#' '.' '.' '.' '.' '.'
              '.' '.' '#' '#' '.' '.' '#' '#' '.' '#'
              '#' '.' '.' '.' '.' '#' '.' '.' '.' '.'
              '.' '#' '.' '#' '#' '.' '.' '#' '.' '.'
              '.' '#' '.' '.' '.' '#' '#' '#' '.' '#'
              '#' '.' '#' '.' '.' '#' '#' '#' '.' '.'
              '.' '#' '.' '#' '.' '.' '.' '#' '.' '.'
              '.' '.' '.' '#' '#' '.' '#' '.' '#' '.' 
              'G' '#' '.' '.' '.' '.' '.' '.' '#' '#']

idx = 81; while idx ~= 10; move = input('Your move?(a,w,d,q)','s'); for idx = find(world == 'v'); switch(move) case 'a' world(idx) = '>'; case 'w' [r,c] = find(world == 'v'); world(r,c) = '.'; world(r+1,c) = 'v'; case 'd' world(idx) = '<'; end end for idx1 = find(world == '^'); switch(move) case 'a' world(idx1) = '<'; case 'w' [r,c] = find(world == '^'); world(r,c) = '.'; world(r-1,c) = '^'; case 'd' world(idx1) = '>'; end end for idx2 = find(world == '<'); switch(move) case 'a' world(idx2) = 'v'; case 'w' [r,c] = find(world == '<'); world(r,c) = '.'; world(r,c-1) = '<'; case 'd' world(idx2) = '^'; end end for idx3 = find(world == '>'); switch(move) case 'a' world(idx3) = '^'; case 'w' [r,c] = find(world == '>'); world(r,c) = '.'; world(r,c+1) = '>'; case 'd' world(idx3) = 'v'; end end clc; disp(world); counter = counter + 1

Answer 1

[Image Analyst]

I didn't really read/understand that code, but in general to skip portions of code you can use "if", break, or continue commands.

http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup