Protoype Question With Error Related Help on Wrong Student Answer

#!/usr/local/bin/perl -- -*- C -*-
use CGI;
$query = new CGI;
print $query->header;
print $query->start_html("q1a.pl, Error Related Help Example");
print $query->start_form;
$ans = 5280;
$wrong_ans = 1/5280;
print "<P> How many feet are there in a mile?",
$query->textfield('stu_ans','',10,30);
print "<P> Is the above answer correct?",$query->submit("Send Answer in For Grading");
print $query->reset;
print $query->end_form;
$returned_ans = $query->param('stu_ans');
if ( $query->param('stu_ans') ne '')
{
	print "<em>Student_answer, </em>$returned_ans";
	$returned_ans =~ s/\\//gi; 
	$returned_ans =~ s/\$//gi; 
	$returned_ans =~ s/\#//gi; 
	$returned_ans =~ s/\~//gi;
	$stu_ans = eval($returned_ans);
	if (eval (($stu_ans - $wrong_ans)**2  ) le 0.000001 ) 
		{print "<em>, was WRONG! Did you get the answer upside down?</EM>
		<IMG SRC=../icons/checkno.gif>"}
		elsif( (($stu_ans - $ans)**2  ) ge 0.01  )
		{print "<em>, was WRONG! </EM>
		<a href=./q1_help.pl>Do you want help?</a>"}
		 else {print "<em>, was RIGHT! </EM>
		<IMG SRC=../icons/check.gif>"};
};
print $query->end_html;

There are several changes to the last program in order to understand what is going one here. First, we have added a `wrong_answer' i.e.,

$wrong_ans = 1/5280;

	if (eval (($stu_ans - $wrong_ans)**2  ) le 0.000001 ) 
		{print "<em>, was WRONG! Did you get the answer upside down?</EM>
		<IMG SRC=../icons/checkno.gif>"}
		elsif( (($stu_ans - $ans)**2  ) ge 0.01  )
		{print "<em>, was WRONG! </EM>
		<a href=./q1_help.pl>Do you want help?</a>"}
		 else {print "<em>, was RIGHT! </EM>
		<IMG SRC=../icons/check.gif>"};
};