of the special variables that you have changed. This is one of the
correct ways to read the whole file at once:
- open my $fh, "foo" or die $!;
+ open my $fh, "<", "foo" or die $!;
local $/; # enable localized slurp mode
my $content = <$fh>;
close $fh;
But the following code is quite bad:
- open my $fh, "foo" or die $!;
+ open my $fh, "<", "foo" or die $!;
undef $/; # enable slurp mode
my $content = <$fh>;
close $fh;
example:
my $content = '';
- open my $fh, "foo" or die $!;
+ open my $fh, "<", "foo" or die $!;
{
local $/;
$content = <$fh>;
=item *
-Various unary functions, including functions like ord() and int(), as well
-as the all file tests (C<-f>, C<-d>) except for C<-t>, which defaults to
-STDIN.
+The following functions:
+
+abs, alarm, chomp, chop, chr, chroot, cos, defined, eval, exp, glob,
+hex, int, lc, lcfirst, length, log, lstat, mkdir, oct, ord, pos, print,
+quotemeta, readlink, readpipe, ref, require, reverse (in scalar context only),
+rmdir, sin, split (on its second argument), sqrt, stat, study, uc, ucfirst,
+unlink, unpack.
=item *
-Various list functions like print() and unlink().
+All file tests (C<-f>, C<-d>) except for C<-t>, which defaults to STDIN.
+See L<perlfunc/-X>
+
=item *
-The pattern matching operations C<m//>, C<s///>, and C<tr///> when used
-without an C<=~> operator.
+The pattern matching operations C<m//>, C<s///> and C<tr///> (aka C<y///>)
+when used without an C<=~> operator.
=item *
=item *
+The implicit variable of given().
+
+=item *
+
The default place to put an input record when a C<< <FH> >>
operation's result is tested by itself as the sole criterion of a C<while>
test. Outside a C<while> test, this will not happen.
As C<$_> is a global variable, this may lead in some cases to unwanted
side-effects. As of perl 5.9.1, you can now use a lexical version of
C<$_> by declaring it in a file or in a block with C<my>. Moreover,
-declaring C<our $> restores the global C<$_> in the current scope.
+declaring C<our $_> restores the global C<$_> in the current scope.
(Mnemonic: underline is understood in certain operations.)
=item ${^MATCH}
X<${^MATCH}>
-This is similar to C<$&> (C<$POSTMATCH>) except that it does not incur the
+This is similar to C<$&> (C<$MATCH>) except that it does not incur the
performance penalty associated with that variable, and is only guaranteed
to return a defined value when the pattern was compiled or executed with
the C</p> modifier.
how many subgroups were in the last successful match. See the
examples given for the C<@-> variable.
+=item %LAST_PAREN_MATCH
+
=item %+
X<%+>
integer. So this:
local $/ = \32768; # or \"32768", or \$var_containing_32768
- open my $fh, $myfile or die $!;
+ open my $fh, "<", $myfile or die $!;
local $_ = <$fh>;
will read a record of no more than 32768 bytes from FILE. If you're
you are outputting to a pipe or socket, such as when you are running
a Perl program under B<rsh> and want to see the output as it's
happening. This has no effect on input buffering. See L<perlfunc/getc>
-for that. (Mnemonic: when you want your pipes to be piping hot.)
+for that. See L<perldoc/select> on how to select the output channel.
+See also L<IO::Handle>. (Mnemonic: when you want your pipes to be piping hot.)
=item IO::Handle->output_field_separator EXPR
sets this variable. This means that the value of C<$!> is meaningful
only I<immediately> after a B<failure>:
- if (open(FH, $filename)) {
+ if (open my $fh, "<", $filename) {
# Here $! is meaningless.
...
} else {
the view of C<$0> the other threads have will not change since they
have their own copies of it.
+If the program has been given to perl via the switches C<-e> or C<-E>,
+C<$0> will contain the string C<"-e">.
+
=item $[
X<$[>
As of release 5 of Perl, assignment to C<$[> is treated as a compiler
directive, and cannot influence the behavior of any other file.
-(That's why you can only assign compile-time constants to it.)
-Its use is highly discouraged.
+(That's why you can only assign compile-time constants to it.) Its
+use is deprecated, and will trigger a warning (if the deprecation
+L<warnings> category is enabled. You did C<use warnings>, right?)
Note that, unlike other compile-time directives (such as L<strict>),
assignment to C<$[> can be seen from outer lexical scopes in the same file.
=item 0x02
-Line-by-line debugging.
+Line-by-line debugging. Causes DB::DB() subroutine to be called for each
+statement executed. Also causes saving source code lines (like 0x400).
=item 0x04
=item 0x400
-Debug assertion subroutines enter/exit.
+Save source code lines into C<@{"_<$filename"}>.
=back
Some bits may be relevant at compile-time only, some at
run-time only. This is a new mechanism and the details may change.
+See also L<perldebguts>.
=item $LAST_REGEXP_CODE_RESULT
X<$^V> X<$PERL_VERSION>
The revision, version, and subversion of the Perl interpreter, represented
-as a string composed of characters with those ordinals. Thus in Perl v5.6.0
-it equals C<chr(5) . chr(6) . chr(0)> and will return true for
-C<$^V eq v5.6.0>. Note that the characters in this string value can
-potentially be greater than 255.
+as a C<version> object.
This variable first appeared in perl 5.6.0; earlier versions of perl will
-see an undefined value.
+see an undefined value. Before perl 5.10.0 $^V was represented as a v-string.
-This can be used to determine whether the Perl interpreter executing a
+$^V can be used to determine whether the Perl interpreter executing a
script is in the right range of versions. (Mnemonic: use ^V for Version
Control.) Example:
projects / p5sagit/p5-mst-13.2.git / blobdiff