+/**
+ * SECTION:gregex
+ * @title: Perl-compatible regular expressions
+ * @short_description: matches strings against regular expressions
+ * @see_also: [Regular expression syntax][glib-regex-syntax]
+ *
+ * The g_regex_*() functions implement regular
+ * expression pattern matching using syntax and semantics similar to
+ * Perl regular expression.
+ *
+ * Some functions accept a @start_position argument, setting it differs
+ * from just passing over a shortened string and setting #G_REGEX_MATCH_NOTBOL
+ * in the case of a pattern that begins with any kind of lookbehind assertion.
+ * For example, consider the pattern "\Biss\B" which finds occurrences of "iss"
+ * in the middle of words. ("\B" matches only if the current position in the
+ * subject is not a word boundary.) When applied to the string "Mississipi"
+ * from the fourth byte, namely "issipi", it does not match, because "\B" is
+ * always false at the start of the subject, which is deemed to be a word
+ * boundary. However, if the entire string is passed , but with
+ * @start_position set to 4, it finds the second occurrence of "iss" because
+ * it is able to look behind the starting point to discover that it is
+ * preceded by a letter.
+ *
+ * Note that, unless you set the #G_REGEX_RAW flag, all the strings passed
+ * to these functions must be encoded in UTF-8. The lengths and the positions
+ * inside the strings are in bytes and not in characters, so, for instance,
+ * "\xc3\xa0" (i.e. "à") is two bytes long but it is treated as a
+ * single character. If you set #G_REGEX_RAW the strings can be non-valid
+ * UTF-8 strings and a byte is treated as a character, so "\xc3\xa0" is two
+ * bytes and two characters long.
+ *
+ * When matching a pattern, "\n" matches only against a "\n" character in
+ * the string, and "\r" matches only a "\r" character. To match any newline
+ * sequence use "\R". This particular group matches either the two-character
+ * sequence CR + LF ("\r\n"), or one of the single characters LF (linefeed,
+ * U+000A, "\n"), VT vertical tab, U+000B, "\v"), FF (formfeed, U+000C, "\f"),
+ * CR (carriage return, U+000D, "\r"), NEL (next line, U+0085), LS (line
+ * separator, U+2028), or PS (paragraph separator, U+2029).
+ *
+ * The behaviour of the dot, circumflex, and dollar metacharacters are
+ * affected by newline characters, the default is to recognize any newline
+ * character (the same characters recognized by "\R"). This can be changed
+ * with #G_REGEX_NEWLINE_CR, #G_REGEX_NEWLINE_LF and #G_REGEX_NEWLINE_CRLF
+ * compile options, and with #G_REGEX_MATCH_NEWLINE_ANY,
+ * #G_REGEX_MATCH_NEWLINE_CR, #G_REGEX_MATCH_NEWLINE_LF and
+ * #G_REGEX_MATCH_NEWLINE_CRLF match options. These settings are also
+ * relevant when compiling a pattern if #G_REGEX_EXTENDED is set, and an
+ * unescaped "#" outside a character class is encountered. This indicates
+ * a comment that lasts until after the next newline.
+ *
+ * When setting the %G_REGEX_JAVASCRIPT_COMPAT flag, pattern syntax and pattern
+ * matching is changed to be compatible with the way that regular expressions
+ * work in JavaScript. More precisely, a lonely ']' character in the pattern
+ * is a syntax error; the '\x' escape only allows 0 to 2 hexadecimal digits, and
+ * you must use the '\u' escape sequence with 4 hex digits to specify a unicode
+ * codepoint instead of '\x' or 'x{....}'. If '\x' or '\u' are not followed by
+ * the specified number of hex digits, they match 'x' and 'u' literally; also
+ * '\U' always matches 'U' instead of being an error in the pattern. Finally,
+ * pattern matching is modified so that back references to an unset subpattern
+ * group produces a match with the empty string instead of an error. See
+ * pcreapi(3) for more information.
+ *
+ * Creating and manipulating the same #GRegex structure from different
+ * threads is not a problem as #GRegex does not modify its internal
+ * state between creation and destruction, on the other hand #GMatchInfo
+ * is not threadsafe.
+ *
+ * The regular expressions low-level functionalities are obtained through
+ * the excellent
+ * [PCRE](http://www.pcre.org/)
+ * library written by Philip Hazel.
+ */