Perl Regex to get the root domain of a URL

Question

How could I get some part of url?

For example:

http://www.facebook.com/xxxxxxxxxxx
http://www.stackoverflow.com/yyyyyyyyyyyyyyyy

I

Answer 1

$a="http://www.stackoverflow.com/yyyyyyyyyyyyyyyy";
if($a=~/\/\/\w+\.(.*)\// )
{   print $1; }
else
{ print "false";  }