$_ = 'http://www.foo.com/';
s/^http:\/\/(.*)\/(.*)/http:\/\/123.1.34.107:8080\/Web/;
print("$_\n");

$_ = 'http://www.foo.com/';
s[^http://(.*)(.*)][http://123.1.34.107:8080];
print("$_\n");