The GNU Awk User’s Guide : GNU Regexp Operators

The GNU #Awk User’s Guide: GNU #Regexp Operators
▻https://www.gnu.org/software/gawk/manual/html_node/GNU-Regexp-Operators.html

3.5 gawk-Specific Regexp Operators

GNU software that deals with regular expressions provides a number of additional regexp operators. These operators are described in this section and are specific to gawk; they are not available in other awk implementations. Most of the additional operators deal with word matching. For our purposes, a word is a sequence of one or more letters, digits, or underscores (‘_’):