unity3d - vert: function return value missing semantics -

i trying running code unity site

shader  "unityexample/vertex , fragment/3-behind bars" {     subshader{             pass{             cgprogram             #pragma vertex vert             #pragma fragment frag              #include "unitycg.cginc"              struct vertout{                 float4 pos: sv_position;                 float4 scrpos;             };              vertout vert(appdata_base v){                 vertout o;                 o.pos = mul(unity_matrix_mvp, v.vertex);                 o.scrpos = computescreenpos(o.pos);                 return o;             }              fixed4 frag(vertout i) : sv_target{                 float2 wcoord  = (i.scrpos.xy/i.scrpos.w);                 fixed4 color;                  if(fmod(20.0 * wcoord.x,2.0)<1.0){                     color = fixed4(wcoord.xy,0.0,1.0);                 } else{                     color = fixed4(0.3,0.3,0.3,1.0);                 }                 return color;             }             endcg         }     } } 

this code showing me error on line

vertout vert(appdata_base v) 

vert: function return value missing semantics

i using unity 4.6

semantics missing scrpos.

float4 scrpos : texcoord0;