of operation work on some other string. The right argument is a search
pattern, substitution, or transliteration. The left argument is what is
supposed to be searched, substituted, or transliterated instead of the default
-$_. The return value indicates the success of the operation. (If the
+$_. The return value indicates the success of the operation. If the
right argument is an expression rather than a search pattern,
substitution, or transliteration, it is interpreted as a search pattern at run
-time. This can be is less efficient than an explicit search, because the
+time. This can be less efficient than an explicit search, because the
pattern must be compiled every time the expression is evaluated.
Binary "!~" is just like "=~" except the return value is negated in
operator is not as well defined for negative operands, but it will
execute faster.
-Binary "x" is the repetition operator. In scalar context, it
-returns a string consisting of the left operand repeated the number of
-times specified by the right operand. In list context, if the left
-operand is a list in parentheses, it repeats the list.
+Binary "x" is the repetition operator. In scalar context or if the left
+operand is not enclosed in parentheses, it returns a string consisting
+of the left operand repeated the number of times specified by the right
+operand. In list context, if the left operand is enclosed in
+parentheses, it repeats the list.
print '-' x 80; # print row of dashes
Binary "<<" returns the value of its left argument shifted left by the
number of bits specified by the right argument. Arguments should be
-integers. (See also L<Integer Arithmetic>.) Shifting more than the
-width of an integer in bits (usually 32 or 64) produces undefined
-(platform dependent) results.
+integers. (See also L<Integer Arithmetic>.)
Binary ">>" returns the value of its left argument shifted right by
the number of bits specified by the right argument. Arguments should
-be integers. (See also L<Integer Arithmetic>.) Shifting more than
-the width of an integer in bits (usually 32 or 64) produces undefined
-(platform dependent) results.
+be integers. (See also L<Integer Arithmetic>.)
=head2 Named Unary Operators
unlink("alpha", "beta", "gamma")
|| (gripe(), next LINE);
-Use "or" for assignment is unlikely to do what you want; see below.
+Using "or" for assignment is unlikely to do what you want; see below.
=head2 Range Operators
Although these are grouped by family, they all have the precedence
of assignment.
-Unlike in C, the assignment operator produces a valid lvalue. Modifying
-an assignment is equivalent to doing the assignment and then modifying
-the variable that was assigned to. This is useful for modifying
-a copy of something, like this:
+Unlike in C, the scalar assignment operator produces a valid lvalue.
+Modifying an assignment is equivalent to doing the assignment and
+then modifying the variable that was assigned to. This is useful
+for modifying a copy of something, like this:
($tmp = $global) =~ tr [A-Z] [a-z];
$a += 2;
$a *= 3;
+Similarly, a list assignment in list context produces the list of
+lvalues assigned to, and a list assignment in scalar context returns
+the number of elements produced by the expression on the right hand
+side of the assignment.
+
=head2 Comma Operator
Binary "," is the comma operator. In scalar context it evaluates
and is useful when the value you are interpolating won't change over
the life of the script. However, mentioning C</o> constitutes a promise
that you won't change the variables in the pattern. If you change them,
-Perl won't even notice. See also L<qr//>.
+Perl won't even notice. See also L<"qr//">.
If the PATTERN evaluates to the empty string, the last
I<successfully> matched regular expression is used instead.
my @compiled = map qr/$_/i, @$patterns;
grep {
my $success = 0;
- foreach my $pat @compiled {
+ foreach my $pat (@compiled) {
$success = 1, last if /$pat/;
}
$success;
qw(foo bar baz)
-is exactly equivalent to the list:
+is semantically equivalent to the list:
- ('foo', 'bar', 'baz')
+ 'foo', 'bar', 'baz'
Some frequently seen examples:
See L<perlfunc/vec> for information on how to manipulate individual bits
in a bit vector.
+=head2 Strings of Character
+
+A literal of the form C<v1.20.300.4000> is parsed as a string composed
+of characters with the specified ordinals. This provides an alternative,
+more readable way to construct strings, rather than use the somewhat less
+readable interpolation form C<"\x{1}\x{14}\x{12c}\x{fa0}">. This is useful
+for representing Unicode strings, and for comparing version "numbers"
+using the string comparison operators, C<cmp>, C<gt>, C<lt> etc.
+
+If there are more than two dots in the literal, the leading C<v> may be
+omitted.
+
+Such literals are accepted by both C<require> and C<use> for doing a version
+check. The C<$^V> special variable also contains the running Perl
+interpreter's version in this form. See L<perlvar/$^V>.
+
=head2 Integer Arithmetic
By default, Perl assumes that it must do most of its arithmetic in
The non-standard modules SSLeay::BN and Math::Pari provide
equivalent functionality (and much more) with a substantial
performance savings.
+
+=cut
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