+Any of these modifiers can be set to apply globally to all regular
+expressions compiled within the scope of a C<use re>. See
+L<re/"'/flags' mode">.
+
+Starting in Perl 5.14, a C<"^"> (caret or circumflex accent) immediately
+after the C<"?"> is a shorthand equivalent to C<d-imsx>. Flags (except
+C<"d">) may follow the caret to override it.
+But a minus sign is not legal with it.
+
+Also, starting in Perl 5.14, are modifiers C<"a">, C<"d">, C<"l">, and
+C<"u">, which for 5.14 may not be used as suffix modifiers.
+
+C<"l"> means to use a locale (see L<perllocale>) when pattern matching.
+The locale used will be the one in effect at the time of execution of
+the pattern match. This may not be the same as the compilation-time
+locale, and can differ from one match to another if there is an
+intervening call of the
+L<setlocale() function|perllocale/The setlocale function>.
+This modifier is automatically set if the regular expression is compiled
+within the scope of a C<"use locale"> pragma. Results are not
+well-defined when using this and matching against a utf8-encoded string.
+
+C<"u"> means to use Unicode semantics when pattern matching. It is
+automatically set if the regular expression is encoded in utf8, or is
+compiled within the scope of a
+L<C<"use feature 'unicode_strings">|feature> pragma (and isn't also in
+the scope of L<C<"use locale">|locale> nor L<C<"use bytes">|bytes>
+pragmas. On ASCII platforms, the code points between 128 and 255 take on their
+Latin-1 (ISO-8859-1) meanings (which are the same as Unicode's), whereas
+in strict ASCII their meanings are undefined. Thus the platform
+effectively becomes a Unicode platform. The ASCII characters remain as
+ASCII characters (since ASCII is a subset of Latin-1 and Unicode). For
+example, when this option is not on, on a non-utf8 string, C<"\w">
+matches precisely C<[A-Za-z0-9_]>. When the option is on, it matches
+not just those, but all the Latin-1 word characters (such as an "n" with
+a tilde). On EBCDIC platforms, which already are equivalent to Latin-1,
+this modifier changes behavior only when the C<"/i"> modifier is also
+specified, and affects only two characters, giving them full Unicode
+semantics: the C<MICRO SIGN> will match the Greek capital and
+small letters C<MU>; otherwise not; and the C<LATIN CAPITAL LETTER SHARP
+S> will match any of C<SS>, C<Ss>, C<sS>, and C<ss>, otherwise not.
+(This last case is buggy, however.)
+
+C<"a"> is the same as C<"u">, except that C<\d>, C<\s>, C<\w>, and the
+Posix character classes are restricted to matching in the ASCII range
+only. That is, with this modifier, C<\d> always means precisely the
+digits C<"0"> to C<"9">; C<\s> means the five characters C<[ \f\n\r\t]>;
+C<\w> means the 63 characters C<[A-Za-z0-9_]>; and likewise, all the
+Posix classes such as C<[[:print:]]> match only the appropriate
+ASCII-range characters. As you would expect, this modifier causes, for
+example, C<\D> to mean the same thing as C<[^0-9]>; in fact, all
+non-ASCII characters match C<\D>, C<\S>, and C<\W>. C<\b> still means
+to match at the boundary between C<\w> and C<\W>, using the C<"a">
+definitions of them (similarly for C<\B>). Otherwise, C<"a"> behaves
+like the C<"u"> modifier, in that case-insensitive matching uses Unicode
+semantics; for example, "k" will match the Unicode C<\N{KELVIN SIGN}>
+under C</i> matching, and code points in the Latin1 range, above ASCII
+will have Unicode semantics when it comes to case-insensitive matching.
+
+C<"d"> means to use the traditional Perl pattern matching behavior.
+This is dualistic (hence the name C<"d">, which also could stand for
+"depends"). When this is in effect, Perl matches utf8-encoded strings
+using Unicode rules, and matches non-utf8-encoded strings using the
+platform's native character set rules. (If the regular expression
+itself is encoded in utf8, Unicode rules are used regardless of the
+target string's encoding.)
+See L<perlunicode/The "Unicode Bug">. It is automatically selected by
+default if the regular expression is compiled neither within the scope
+of a C<"use locale"> pragma nor a <C<"use feature 'unicode_strings">
+pragma.
+
+Note that the C<a>, C<d>, C<l>, C<p>, and C<u> modifiers are special in
+that they can only be enabled, not disabled, and the C<d>, C<l>, and
+C<u> modifiers are mutually exclusive: specifying one de-specifies the
+others, and a maximum of one may appear in the construct. Thus, for
+example, C<(?-p)>, C<(?-d:...)>, and C<(?dl:...)> will warn when
+compiled under C<use warnings>.
+
+Note also that the C<p> modifier is special in that its presence
+anywhere in a pattern has a global effect.