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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