The you.x part does not make sense, but I've got the code working like this:
Code:

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var i=0; var k=0; var tttt[3];

var min_val=500; var min_i;

while (i < ent_vertices (my))
{ 
	vec_for_vertex(tttt,my,i);
	//k=vec_dist(tttt,you.x);
	k=vec_dist(tttt,target.x);
	if(k<min_val) 
         {min_val=k; min_i=i;}
	i+=1;
}

vec_for_mesh(temp,my,min_i);
vec_scale(temp,0.2);
vec_to_mesh(temp,my,min_i);
ent_fixnormals(my,0);

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