Secent method implementation using perl language

#Md. Alamgir Hossain
#Dept. of Computer Science & Engineering
#Jessore University of Science & Technology
#Secent method implementation us   ing perl language......


#--------------------The given function ---------------------------
sub secentMethod
{
($x)=@_;
#return (($x*$x)-(5*$x)+2);
#return (2*$x-3-cos($x));
#return (($x*$x*$x) - (21*$x)+3500);
#return ($x*$x-5*$x+2);
#return ($x*$x)-(4*$x)-10;
return ($x*$x*$x)-(4*$x)-9;

}
$x0,$x1,$l1,$l2,$r,$f1,$f2,$f3,$iteration=5,$cnt=1;

#--------------------Finding a and b----------------------

    for($k=-20;$k<=$iteration;$k++){
        if(&secentMethod($k)>0){
            if(&secentMethod($k+1)<0){
                $x0=$k;
                $x1=$k+1;

                print "a = ";
                print ($x0);
                print " and F(x) is positive. b = ";
                print ($x1);
                print ", and F(x) is Negative \n\n";
                last;
            }
        }
        if(&secentMethod($k)<0){
            if(secentMethod($k+1)>0){
                $x0=$k;
                $x1=$k+1;
                print "a = ";
                print ($x0);
                print " and F(x) is Negative. b = ";

                print ($x1);
                print " and F(x) is Positive \n\n";
                last;
            }
        }


}

print "---------------------------Iteraation part-------------------------------\n\n";

$l1=   $x0;
$l2=   $x1;

#------Finding root after one by one iteration---------------

    for($i=1;$i<=$iteration;$i++){
              $first=(&secentMethod($l2)*($l2-$l1));
              $second=(&secentMethod($l2)-&secentMethod($l1));
              $l3=$l2-($first/$second);
              #$l3=$l2- ((&secentMethod($l2)*($l2-$l1))/(&secentMethod($l2)-&secentMethod($l1)));
              #$pr=abs(($l3-$l2)/($l3));
              print "After iteration ";
              print ($i);
              print " The root is : ";
              print ($l3);
              print "\n";
              $l1=$l2;
              $l2=$l3;
  }
  #-----------------------------Approximate root or Ans root-----------------------------

  print "\nApproximate root is : ";
  print ($l3);
  print "\n";
 
exit;