Add transformations in backward regression using p value

Question

Good Night, I was looking at the method of selection of variables, found in this link:

Stepwise regression using p-values to drop variables with nonsignificant p-values

And I wanted to add some transformations before deleting the variable ... example (root, log, power, ...)

I tried to add in the linked code (Joris Meys) the following command:

while (T) {    
           trans <- I(dropvar[1])^2)
           testF2 <-add1 (model, trans, test = "F")
          }
if(verbose){
          cat("-------------STEP ",counter,"-------------\n",
          "The drop statistics : \n")
          print(test)
      }

if(pval[i]<sig) break # stops the loop if var to remove is significant

      if(verbose){
         cat("\n--------\nTerm added in step",counter,":",dropvar,"\n--------\n\n")              
      }

But the dropvar variable is as string. Can someone help me?