#!/usr/bin/
use warnings;

print "this program will attempt to compute the circumfrence of a circle.\n";
print "\n";
print "Please enter in the radius of your circle.\n";
$radius = <STDIN>;

until ($radius ne "\n") {
    print "please enter a number ";
    $radius = <STDIN>;
}
print 2 * 3.141592654 * $radius;
print "\n";