This is a work derived from Russ Cox's RE2 in Go, whose license
http://golang.org/LICENSE is as follows:

Copyright (c) 2009 The Go Authors. All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

   * Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.

   * Redistributions in binary form must reproduce the above copyright
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     the documentation and/or other materials provided with the
     distribution.

   * Neither the name of Google Inc. nor the names of its contributors
     may be used to endorse or promote products derived from this
     software without specific prior written permission.

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