Don't use a regex for this. Use the appropriate tool, use URI.

use URI;
my $my_url = 'http://www.perlmonks.org:8080/index.pl?whatever';
my $uri = URI->new($my_url);
my $host = $uri->host();
[download]

Or, in one go (to illustrate that you do not need to name your objects if you don't need them to stick around):

use URI;
my $host = URI->new('http://www.perlmonks.org:8080/index.pl?whatever')
+->host;
[download]

- Yes, I reinvent wheels.
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