gawk: Regexp Constants

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1 6.1.1.3 Regular Expression Constants
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1 A "regexp constant" is a regular expression description enclosed in
1 slashes, such as '/^beginning and end$/'.  Most regexps used in 'awk'
1 programs are constant, but the '~' and '!~' matching operators can also
1 match computed or dynamic regexps (which are typically just ordinary
1 strings or variables that contain a regexp, but could be more complex
1 expressions).
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