=over
-=item A sigil, followed solely by digits matching \p{POSIX_Digit}, like C<$0>,
-C<$1>, or C<$10000>.
-
-=item A sigil, followed by either a caret and a single POSIX uppercase letter,
-like C<$^V> or C<$^W>, or a sigil followed by a literal control character
-matching the C<\p{POSIX_Cntrl}> property.
-Due to a historical oddity, if not
-running under C<use utf8>, the 128 extra controls in the C<[0x80-0xff]> range
-may also be used in length one variables. The use of a literal control
-character is deprecated. Support for this form will be removed in a future
-version of perl.
-
-=item Similar to the above, a sigil, followed by bareword text in brackets,
-where the first character is either a caret followed by an uppercase letter,
-or a literal control, like C<${^GLOBAL_PHASE}> or C<${\7LOBAL_PHASE}>. The use
-of a literal control character is deprecated. Support for this form will be
-removed in a future version of perl.
-
-=item A sigil followed by a single character matching the C<\p{POSIX_Punct}>
-property, like C<$!> or C<%+>.
+=item *
+
+A sigil, followed solely by digits matching C<\p{POSIX_Digit}>, like
+C<$0>, C<$1>, or C<$10000>.
+
+=item *
+
+A sigil, followed by either a caret and a single POSIX uppercase letter,
+like C<$^V> or C<$^W>, or a sigil followed by a literal non-space,
+non-C<NUL> control character matching the C<\p{POSIX_Cntrl}> property.
+Due to a historical oddity, if not running under C<use utf8>, the 128
+characters in the C<[0x80-0xff]> range are considered to be controls,
+and may also be used in length-one variables. However, the use of
+non-graphical characters is deprecated as of v5.22, and support for them
+will be removed in a future version of perl. ASCII space characters and
+C<NUL> already aren't allowed, so this means that a single-character
+variable name with that name being any other C0 control C<[0x01-0x1F]>,
+or C<DEL> will generate a deprecated warning. Already, under C<"use
+utf8">, non-ASCII characters must match C<Perl_XIDS>. As of v5.22, when
+not under C<"use utf8"> C1 controls C<[0x80-0x9F]>, NO BREAK SPACE, and
+SOFT HYPHEN (C<SHY>)) generate a deprecated warning.
+
+=item *
+
+Similar to the above, a sigil, followed by bareword text in brackets,
+where the first character is either a caret followed by an uppercase
+letter, like C<${^GLOBAL_PHASE}> or a non-C<NUL>, non-space literal
+control like C<${\7LOBAL_PHASE}>. Like the above, when not under
+C<"use utf8">, the characters in C<[0x80-0xFF]> are considered controls, but as
+of v5.22, the use of any that are non-graphical are deprecated, and as
+of v5.20 the use of any ASCII-range literal control is deprecated.
+Support for these will be removed in a future version of perl.
+
+=item *
+
+A sigil followed by a single character matching the C<\p{POSIX_Punct}>
+property, like C<$!> or C<%+>, except the character C<"{"> doesn't work.
=back
Note that as of Perl 5.20, literal control characters in variable names
-are deprecated.
+are deprecated; and as of Perl 5.22, any other non-graphic characters
+are also deprecated.
=head2 Context
X<context> X<scalar context> X<list context>
($dev, $ino, undef, undef, $uid, $gid) = stat($file);
+As of Perl 5.22, you can also use C<(undef)x2> instead of C<undef, undef>.
+(You can also do C<($x) x 2>, which is less useful, because it assigns to
+the same variable twice, clobbering the first value assigned.)
+
List assignment in scalar context returns the number of elements
produced by the expression on the right side of the assignment:
s/(\w+)/\u\L$1/g; # "titlecase" words
}
-A slice of an empty list is still an empty list. Thus:
-
- @a = ()[1,0]; # @a has no elements
- @b = (@a)[0,1]; # @b has no elements
-
-But:
-
- @a = (1)[1,0]; # @a has two elements
- @b = (1,undef)[1,0,2]; # @b has three elements
-
-More generally, a slice yields the empty list if it indexes only
-beyond the end of a list:
+As a special exception, when you slice a list (but not an array or a hash),
+if the list evaluates to empty, then taking a slice of that empty list will
+always yield the empty list in turn. Thus:
- @a = (1)[ 1,2]; # @a has no elements
- @b = (1)[0,1,2]; # @b has three elements
+ @a = ()[0,1]; # @a has no elements
+ @b = (@a)[0,1]; # @b has no elements
+ @c = (sub{}->())[0,1]; # @c has no elements
+ @d = ('a','b')[0,1]; # @d has two elements
+ @e = (@d)[0,1,8,9]; # @e has four elements
+ @f = (@d)[8,9]; # @f has two elements
This makes it easy to write loops that terminate when a null list
is returned:
- while ( ($home, $user) = (getpwent)[7,0]) {
+ while ( ($home, $user) = (getpwent)[7,0] ) {
printf "%-8s %s\n", $user, $home;
}
https://perl5.git.perl.org / perl5.git / blobdiff