int( <STDIN> )
-the integer operation provides scalar context for the E<lt><gt>
+the integer operation provides scalar context for the <>
operator, which responds by reading one line from STDIN and passing it
back to the integer operation, which will then find the integer value
of that line and return that. If, on the other hand, you say
sort( <STDIN> )
-then the sort operation provides list context for E<lt><gt>, which
+then the sort operation provides list context for <>, which
will proceed to read every line available up to the end of file, and
pass that list of lines back to the sort routine, which will then
sort those lines and return them as a list to whatever the context
context. Assignment to a list (or slice, which is just a list
anyway) also evaluates the righthand side in list context.
-When you use Perl's B<-w> command-line option, you may see warnings
+When you use the C<use warnings> pragma or Perl's B<-w> command-line
+option, you may see warnings
about useless uses of constants or functions in "void context".
Void context just means the value has been discarded, such as a
statement containing only C<"fred";> or C<getpwuid(0);>. It still
0xff # hex
0377 # octal
0b011011 # binary
- v102.111.111 # string (made of characters "f", "o", "o")
String literals are usually delimited by either single or double
quotes. They work much like quotes in the standard Unix shells:
substitution; single-quoted strings are not (except for C<\'> and
C<\\>). The usual C-style backslash rules apply for making
characters such as newline, tab, etc., as well as some more exotic
-forms. See L<perlop/"Quote and Quotelike Operators"> for a list.
+forms. See L<perlop/"Quote and Quote-like Operators"> for a list.
Hexadecimal, octal, or binary, representations in string literals
(e.g. '0xff') are not automatically converted to their integer
for representing Unicode strings, and for comparing version "numbers"
using the string comparison operators, C<cmp>, C<gt>, C<lt> etc.
If there are two or more dots in the literal, the leading C<v> may be
-omitted. Such literals are accepted by both C<require> and C<use> for
+omitted.
+
+ print v9786; # prints UTF-8 encoded SMILEY, "\x{263a}"
+ print v102.111.111; # prints "foo"
+ print 102.111.111; # same
+
+Such literals are accepted by both C<require> and C<use> for
doing a version check. The C<$^V> special variable also contains the
running Perl interpreter's version in this form. See L<perlvar/$^V>.
be treated as if it were a quoted string. These are known as
"barewords". As with filehandles and labels, a bareword that consists
entirely of lowercase letters risks conflict with future reserved
-words, and if you use the B<-w> switch, Perl will warn you about any
+words, and if you use the C<use warnings> pragma or the B<-w> switch,
+Perl will warn you about any
such words. Some people may wish to outlaw barewords entirely. If you
say
braces as above.
A line-oriented form of quoting is based on the shell "here-document"
-syntax. Following a C<E<lt>E<lt>> you specify a string to terminate
+syntax. Following a C<< << >> you specify a string to terminate
the quoted material, and all lines following the current line down to
the terminating string are the value of the item. The terminating
string may be either an identifier (a word), or some quoted text. If
quoted, the type of quotes you use determines the treatment of the
text, just as in regular quoting. An unquoted identifier works like
-double quotes. There must be no space between the C<E<lt>E<lt>> and
+double quotes. There must be no space between the C<< << >> and
the identifier. (If you put a space it will be treated as a null
identifier, which is valid, and matches the first empty line.) The
terminating string must appear by itself (unquoted and with no
parameters lists and return lists from functions) always flatten out into
key/value pairs. That's why it's good to use references sometimes.
-It is often more readable to use the C<=E<gt>> operator between key/value
-pairs. The C<=E<gt>> operator is mostly just a more visually distinctive
+It is often more readable to use the C<< => >> operator between key/value
+pairs. The C<< => >> operator is mostly just a more visually distinctive
synonym for a comma, but it also arranges for its left-hand operand to be
interpreted as a string--if it's a bareword that would be a legal identifier.
This makes it nice for initializing hashes:
In other words, C<*FH> must be used to create new symbol table entries;
C<*foo{THING}> cannot. When in doubt, use C<*FH>.
+All functions that are capable of creating filehandles (open(),
+opendir(), pipe(), socketpair(), sysopen(), socket(), and accept())
+automatically create an anonymous filehandle if the handle passed to
+them is an uninitialized scalar variable. This allows the constructs
+such as C<open(my $fh, ...)> and C<open(local $fh,...)> to be used to
+create filehandles that will conveniently be closed automatically when
+the scope ends, provided there are no other references to them. This
+largely eliminates the need for typeglobs when opening filehandles
+that must be passed around, as in the following example:
+
+ sub myopen {
+ open my $fh, "@_"
+ or die "Can't open '@_': $!";
+ return $fh;
+ }
+
+ {
+ my $f = myopen("</etc/motd");
+ print <$f>;
+ # $f implicitly closed here
+ }
+
Another way to create anonymous filehandles is with the Symbol
module or with the IO::Handle module and its ilk. These modules
have the advantage of not hiding different types of the same name