=item Empty \%c in regex; marked by S<<-- HERE> in m/%s/
+=item Empty \%c{}
+
=item Empty \%c{} in regex; marked by S<<-- HERE> in m/%s/
-(F) C<\p> and C<\P> are used to introduce a named Unicode property, as
-described in L<perlunicode> and L<perlre>. You used C<\p> or C<\P> in
-a regular expression without specifying the property name.
+(F) You used something like C<\b{}>, C<\B{}>, C<\o{}>, C<\p>, C<\P>, or
+C<\x> without specifying anything for it to operate on.
+
+Unfortunately, for backwards compatibility reasons, an empty C<\x> is
+legal outside S<C<use re 'strict'>> and expands to a NUL character.
+
+=item Empty (?) without any modifiers in regex; marked by <-- HERE in m/%s/
+
+(W regexp) (only under C<S<use re 'strict'>>)
+C<(?)> does nothing, so perhaps this is a typo.
=item ${^ENCODING} is no longer supported
(F) Named Unicode character escapes (C<\N{...}>) may return a
multi-character sequence. Even though a character class is
supposed to match just one character of input, perl will match the
-whole thing correctly, except when the class is inverted (C<[^...]>),
-or the escape is the beginning or final end point of a range. The
-mathematically logical behavior for what matches when inverting
-is very different from what people expect, so we have decided to
-forbid it. Similarly unclear is what should be generated when the
-C<\N{...}> is used as one of the end points of the range, such as in
+whole thing correctly, except under certain conditions. These currently
+are
- [\x{41}-\N{ARABIC SEQUENCE YEH WITH HAMZA ABOVE WITH AE}]
-
-What is meant here is unclear, as the C<\N{...}> escape is a sequence
-of code points, so this is made an error.
-
-=item \N{NAME} must be resolved by the lexer in regex; marked by
-S<<-- HERE> in m/%s/
+=over 4
-(F) When compiling a regex pattern, an unresolved named character or
-sequence was encountered. This can happen in any of several ways that
-bypass the lexer, such as using single-quotish context, or an extra
-backslash in double-quotish:
+=item When the class is inverted (C<[^...]>)
- $re = '\N{SPACE}'; # Wrong!
- $re = "\\N{SPACE}"; # Wrong!
- /$re/;
+The mathematically logical behavior for what matches when inverting
+is very different from what people expect, so we have decided to
+forbid it.
-Instead, use double-quotes with a single backslash:
+=item The escape is the beginning or final end point of a range
- $re = "\N{SPACE}"; # ok
- /$re/;
+Similarly unclear is what should be generated when the
+C<\N{...}> is used as one of the end points of the range, such as in
-The lexer can be bypassed as well by creating the pattern from smaller
-components:
+ [\x{41}-\N{ARABIC SEQUENCE YEH WITH HAMZA ABOVE WITH AE}]
- $re = '\N';
- /${re}{SPACE}/; # Wrong!
+What is meant here is unclear, as the C<\N{...}> escape is a sequence
+of code points, so this is made an error.
-It's not a good idea to split a construct in the middle like this, and
-it doesn't work here. Instead use the solution above.
+=item In a regex set
-Finally, the message also can happen under the C</x> regex modifier when the
-C<\N> is separated by spaces from the C<{>, in which case, remove the spaces.
+The syntax S<C<(?[ ])>> in a regular expression yields a list of
+single code points, none can be a sequence.
- /\N {SPACE}/x; # Wrong!
- /\N{SPACE}/x; # ok
+=back
=item No %s allowed while running setuid
of Perl. Check the #! line, or manually feed your script into Perl
yourself.
-=item (?[...]) not valid in locale in regex; marked by S<<-- HERE> in m/%s/
-
-(F) C<(?[...])> cannot be used within the scope of a C<S<use locale>> or with
-an C</l> regular expression modifier, as that would require deferring
-to run-time the calculation of what it should evaluate to, and it is
-regex compile-time only.
-
=item no UTC offset information; assuming local time is UTC
(S) A warning peculiar to VMS. Perl was unable to find the local
subroutine has been aliased, the subroutine's original name will be shown,
regardless of what name the caller used.
+=item Too many nested open parens in regex; marked by <-- HERE in m/%s/
+
+(F) You have exceeded the number of open C<"("> parentheses that haven't
+been matched by corresponding closing ones. This limit prevents eating
+up too much memory. It is initially set to 1000, but may be changed by
+setting C<${^RE_COMPILE_RECURSION_LIMIT}> to some other value. This may
+need to be done in a BEGIN block before the regular expression pattern
+is compiled.
+
=item Too many )'s
(A) You've accidentally run your script through B<csh> instead of Perl.
=item Variable length lookbehind not implemented in regex m/%s/
-(F) Lookbehind is allowed only for subexpressions whose length is fixed and
+(F) B<This message no longer should be raised as of Perl 5.30.> It is
+retained in this document as a convenience for people using an earlier
+Perl version.
+
+In Perl 5.30 and earlier, lookbehind is allowed
+only for subexpressions whose length is fixed and
known at compile time. For positive lookbehind, you can use the C<\K>
regex construct as a way to get the equivalent functionality. See
L<(?<=pattern) and \K in perlre|perlre/\K>.
https://perl5.git.perl.org / perl5.git / blobdiff