Return information about the first byte of any matched
string, for a non-anchored pattern. (This option used to be
called PCRE_INFO_FIRSTCHAR; the old name is still
recognized for backwards compatibility.)
If there is a fixed first byte, e.g. from a pattern such as
(cat|cow|coyote), it is returned in the integer pointed to
by where. Otherwise, if either
(a) the pattern was compiled with the PCRE_MULTILINE
option, and every branch starts with "^" , or
(b) every branch of the pattern starts with ".*"
and PCRE_DOTALL is not set (if it were set, the pattern
would be anchored),
-1 is returned, indicating that the pattern matches
only at the start of a subject string or after any newline
within the string. Otherwise -2 is returned. For
anchored patterns, -2 is returned.
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