#### 10.3.2 Flags for POSIX Regular Expressions ¶

These are the bit flags that you can use in the cflags operand when compiling a regular expression with `regcomp`.

`REG_EXTENDED` ¶

  Treat the pattern as an extended regular expression, rather than as a basic regular expression.

`REG_ICASE` ¶

  Ignore case when matching letters.

`REG_NOSUB` ¶

  Don’t bother storing the contents of the matchptr array.

`REG_NEWLINE` ¶

  Treat a newline in string as dividing string into multiple lines, so that ‘`$`’ can match before the newline and ‘`^`’ can match after. Also, don’t permit ‘`.`’ to match a newline, and don’t permit ‘`[^…]`’ to match a newline.

  Otherwise, newline acts like any other ordinary character.