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Perl - Operators Precedence



Perl Operators Precedence

Operator precedence (order of operations) is a collection of rules that reflect conventions about which procedures to perform first in order to evaluate a given expression.

For example, multiplication has higher precedence than addition. Thus, the expression 1 + 2 × 3 is interpreted to have the value 1 + (2 × 3) = 7, and not (1 + 2) × 3 = 9. When exponent is used in the expression, it has precedence over both addition and multiplication. Thus 3 + 52 = 28 and 3 × 52 = 75.

Operator Associativity

Operator associativity is the direction in which an expression is evaluated. For example:

$x = 10;
$y = 20;

#associativity of = operator is
#Left to Right, hence x will become 20
$x = $y;

As the associativity of = is left to right. Hence x is assigned the value of y.

Example:

The example below illustrates the operator precedence in Perl.

#evaluates 5 * 2 first
$retval1 = 15 - 5 * 2;

#above expression is equivalent to
$retval2 = 15 - (5 * 2);

#forcing compiler to evaluate 15 - 5 first
$retval3 = (15 - 5) * 2;

print("15 - 5 * 2 = $retval1\n");
print("15 - (5 * 2) = $retval2\n");
print("(15 - 5) * 2 = $retval3\n");

The output of the above code will be:

15 - 5 * 2 = 5
15 - (5 * 2) = 5
(15 - 5) * 2 = 20

Perl Operators Precedence Table

The following table lists the precedence and associativity of Perl operators. Operators are listed top to bottom, in descending precedence. Operators with higher precedence are evaluated before operators with relatively lower precedence. When operators have the same precedence, associativity of the operators determines the order in which the operations are performed.

PrecedenceOperatorDescriptionAssociativity
25terms and list operatorsterms and list operators (leftward)Left to Right
24->Arrow operator
23++a  --aPrefix increment, Prefix decrementnon-associative
a++  a--Postfix increment, Postfix decrement
22**Exponentiation operatorRight to Left
21!Logical NOT
~Bitwise NOT
~.Bitwise string NOT
\Reference operator
+a  -aUnary plus and minus
20=~  !~Pattern matching operatorsLeft to Right
19*  /  %Multiplication, Division, Remainder
xRepetition operator
18+  -  .Addition, Subtraction, Concatenating operator
17<<  >>Bitwise left shift and right shift
16Named unary operatorsNamed unary operatorsnon-associative
15isaClass instance Operator
14<  <=  >  >=Less than, Less than or equal, Greater than, and Greater than or equalchained
lt  le  gt  geString comparison operators: Less than, Less than or equal, Greater than, and Greater than or equalchained
13==  !=Equality and inequality operatorchain/na
eq  neString equality and inequality operator
<=>Two sided comparison operator
cmpString two sided comparison operator
~~Smartmatch operator
12&  &.Bitwise AND, Bitwise string ANDLeft to Right
11|  |.Bitwise OR, Bitwise string OR
^  ^.Bitwise XOR, Bitwise string XOR
10&&C-style Logical AND operator
9||C-style Logical OR operator
//Perl-style Logical OR operator
8..Range operatornon-associative
...yada-yada operator
7a?b:cternary (conditional) operatorRight to Left
6=Direct assignment
+=  -=  *=  /=  %=  **=Compound assignment by addition, subtraction, multiplication, division, remainder, and exponentiation
<<=  >>=Compound assignment by Bitwise left shift and right shift
&=  ^=  |=Compound assignment by Bitwise AND, XOR and OR
&.=  ^.=  |.=Compound assignment by Bitwise string AND, XOR and OR
gotogoto statement
lastlast statement
nextnext statement
redoredo statement
dumpdump statement
5,  =>Comma operatorsLeft to Right
4list operatorslist operators (rightward)non assoc
3notLogical NOTRight to Left
2andLogical ANDLeft to Right
1orLogical OR
xorBitwise XOR

❮ Perl - Operators

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