@includeって*.example.com/*ってな風に書けないのか？

Greasemonkey

// @include *
// @exclude http://diveintogreasemonkey.org/*
// @exclude http://www.diveintogreasemonkey.org/*

These lines tell Greasemonkey on which sites you want your user script to execute. Both specify a URL, with the * character as a simple wildcard for part of the domain name or path. In this case, we are telling Greasemonkey to execute the Hello World script on all sites except http://diveintogreasemonkey.org/ and http://www.diveintogreasemonkey.org/. Excludes take precedence over includes, so even though http://diveintogreasemonkey.org/download/ matches * (all sites), it will be excluded because it also matches http://diveintogreasemonkey.org/*.

@include and @exclude are optional. You may specify as many included and excluded URLs as you need, but you must specify each on its own line. If neither is specified, Greasemonkey will execute your user script on all sites (as if you had specified @include *).

http://diveintogreasemonkey.org/helloworld/metadata.html

のかなー・・・
まぁこうかなーとも考えたんだけど、

if (!window.document.baseURI.match(/example.com/i)){
  return;
}

@includeもこんなカンジの実装なのかな？

追記

いや、書けた。