=head1 DESCRIPTION
+In Perl, the operator determines what operation is performed,
+independent of the type of the operands. For example C<$a + $b>
+is always a numeric addition, and if C<$a> or C<$b> do not contain
+numbers, an attempt is made to convert them to numbers first.
+
+This is in contrast to many other dynamic languages, where the
+operation is determined by the type of the first argument. It also
+means that Perl has two versions of some operators, one for numeric
+and one for string comparison. For example C<$a == $b> compares
+two numbers for equality, and C<$a eq $b> compares two strings.
+
+There are a few exceptions though: C<x> can be either string
+repetition or list repetition, depending on the type of the left
+operand, and C<&>, C<|> and C<^> can be either string or numeric bit
+operations.
+
=head2 Operator Precedence and Associativity
X<operator, precedence> X<precedence> X<associativity>
and the left side must be either an object (a blessed reference)
or a class name (that is, a package name). See L<perlobj>.
+The dereferencing cases (as opposed to method-calling cases) are
+somewhat extended by the experimental C<postderef> feature. For the
+details of that feature, consult L<perlref/Postfix Dereference Syntax>.
+
=head2 Auto-increment and Auto-decrement
X<increment> X<auto-increment> X<++> X<decrement> X<auto-decrement> X<-->
binary C<~~> does a "smartmatch" between its arguments. This is mostly
used implicitly in the C<when> construct described in L<perlsyn>, although
not all C<when> clauses call the smartmatch operator. Unique among all of
-Perl's operators, the smartmatch operator can recurse.
+Perl's operators, the smartmatch operator can recurse. The smartmatch
+operator is L<experimental|perlpolicy/experimental> and its behavior is
+subject to change.
It is also unique in that all other Perl operators impose a context
(usually string or numeric context) on their operands, autoconverting
=head2 Bitwise And
X<operator, bitwise, and> X<bitwise and> X<&>
-Binary "&" returns its operands ANDed together bit by bit.
-(See also L<Integer Arithmetic> and L<Bitwise String Operators>.)
+Binary "&" returns its operands ANDed together bit by bit. Although no
+warning is currently raised, the result is not well defined when this operation
+is performed on operands that aren't either numbers (see
+L<Integer Arithmetic>) or bitstrings (see L<Bitwise String Operators>).
Note that "&" has lower priority than relational operators, so for example
the parentheses are essential in a test like
X<bitwise xor> X<^>
Binary "|" returns its operands ORed together bit by bit.
-(See also L<Integer Arithmetic> and L<Bitwise String Operators>.)
Binary "^" returns its operands XORed together bit by bit.
-(See also L<Integer Arithmetic> and L<Bitwise String Operators>.)
+
+Although no warning is currently raised, the results are not well
+defined when these operations are performed on operands that aren't either
+numbers (see L<Integer Arithmetic>) or bitstrings (see L<Bitwise String
+Operators>).
Note that "|" and "^" have lower priority than relational operators, so
for example the brackets are essential in a test like
However, because there are I<many> other lowercase Greek characters than
just those, to match lowercase Greek characters in a regular expression,
-you would use the pattern C</(?:(?=\p{Greek})\p{Lower})+/>.
+you could use the pattern C</(?:(?=\p{Greek})\p{Lower})+/> (or the
+L<experimental feature|perlrecharclass/Extended Bracketed Character
+Classes> C<S</(?[ \p{Greek} & \p{Lower} ])+/>>).
Because each operand is evaluated in integer form, C<2.18 .. 3.14> will
return two elements in list context.
beyond) is being used, the case map used by C<\l>, C<\L>, C<\u>, and
C<\U> is as defined by Unicode. That means that case-mapping
a single character can sometimes produce several characters.
-Under C<use locale>, C<\F> produces the same results as C<\L>.
+Under C<use locale>, C<\F> produces the same results as C<\L>
+for all locales but a UTF-8 one, where it instead uses the Unicode
+definition.
All systems use the virtual C<"\n"> to represent a line terminator,
called a "newline". There is no such thing as an unvarying, physical
explicitly using it.
The last four modifiers listed above, added in Perl 5.14,
-control the character set semantics, but C</a> is the only one you are likely
+control the character set rules, but C</a> is the only one you are likely
to want to specify explicitly; the other three are selected
automatically by various pragmas.
https://perl5.git.perl.org / perl5.git / blobdiff