proc testp (poly p)
{
  def BR = basering;
 
  // Set up new ring and make it the active ring:
  //====================================
  list L = ringlist(basering);
  int s = size(L[2]);   // number of variables
  L[2][s+1] = "@t";     // add new variable with name @t
  int m = size(L[3]);   // number of blocks in def. of ordering
  L[3][m+1] = list("lp",intvec(1));  // implement product ordering
  def newRing = ring(L);
  setring newRing;

  // Compute in the new basering:
  //=========================
  ideal I = @t^2*imap(BR,p), @t^2+var(1)+var(2);
  I = eliminate(I,@t);  // output does not depend on @t
             
  // Transfer results to the previous basering:
  //==================================
  setring BR;
  ideal I = imap(newRing,I);

  return(I);
}