Outside a character class, a dot in the pattern matches any one
character in the subject string except (by default) a character
that signifies the end of a line.
When a line ending is defined as a single character, dot never
matches that character; when the two-character sequence CRLF is
used, dot does not match CR if it is immediately followed by LF,
but otherwise it matches all characters (including isolated CRs
and LFs). When any Unicode line endings are being recognized, dot
does not match CR or LF or any of the other line ending
characters.
The behaviour of dot with regard to newlines can be changed. If
the PCRE_DOTALL option is set, a dot matches any one character,
without exception. If the two-character sequence CRLF is present
in the subject string, it takes two dots to match it.
The handling of dot is entirely independent of the handling of
circumflex and dollar, the only relationship being that they both
involve newlines. Dot has no special meaning in a character
class.
The escape sequence \N behaves like a dot, except that it is not
affected by the PCRE_DOTALL option. In other words, it matches
any character except one that signifies the end of a line. Perl
also uses \N to match characters by name; PCRE does not support
this.
