Performance optimization: Reuse Pattern instance

[wcarmon]

Pattern Instances are immutable and are safe for use by multiple concurrent threads...

See https://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html

[coveralls]

Pull Request Test Coverage Report for Build 87

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.1%) to 23.451%

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Totals
Change from base Build 86:	-0.1%
Covered Lines:	140
Relevant Lines:	597

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💛 - Coveralls