Options for Go Regular Expressions

Regular expressions can have options (also known as flags) that modify their behavior. Each engine supports a different set of options.

Option	Description	Backend value	Portable value
posix	Use `CompilePOSIX` instead of `Compile`	posix	(not portable)

The posix option is really a separate API call (CompilePOSIX). Other option need to be specified in the regex pattern.