First off, we'll need some new HTML to gather a number of feet. Let's use another text box. It should look something like this:
<INPUT TYPE="TEXT" SIZE="10" NAME="feet">
Next up we'll need to use that value to figure the result. First we need to convert the feet to inches and then convert the inches to centimeters. I think we can do that all on one math line. How about this:
print "You entered $FORM{feet} feet. That would be ";
print ($FORM{feet}/12) / 2.2;
print " centimeters.";