You need to look into $mid() (/help $mid)
Code:
  var %a = 11001010000001111010101100010111
  %ip.1 = $mid(%a,1,8)
  %ip.2 = $mid(%a,9,8)
  %ip.3 = $mid(%a,17,8)
  %ip.4 = $mid(%a,25)