Emacs regex. This is specifically for emacs use!

Describes bash regex used in =~ operator, like: if [[ $str =~ _[a-z]+ ]]; then ...

Describes bash regex used in =~ operator, like: if [[ $str =~ _[a-z]+ ]]; then ...

Describes bash regex used in =~ operator, like: if [[ $str =~ _[a-z]+ ]]; then ...

Describes STANDARD regular expressions, that generally work in languages: AWK, Java, Python, Go, Javascript, also possibly GREP BUT NOT emacs or bash