BEGIN {
   eval("
      use LWP::UserAgent ();
      use HTTP::Request::Common;
   ");

   if ($@) {
      ...
   }
}

...

##</code><code>##

BEGIN {
   eval {
      require LWP::UserAgent;
      require HTTP::Request::Common;
      import HTTP::Request::Common;
   };

   if ($@) {
      ...
   }
}

...