Perl Operators

Operators are symbols that tell the compiler to perform specific mathematical or logical operations, such as: 3+2=5.

The Perl language has a rich set of built-in operators. Let's look at the commonly used ones:

• Arithmetic Operators
• Comparison Operators
• Logical Operators
• Assignment Operators
• Bitwise Operators
• Quote Operators
• Other Operators
• Operator Precedence

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Arithmetic Operators

In the following table examples, we set variable $a to 10 and $b to 20.

Operator	Description	Example
+	Addition operation	$a + $b result is 30
-	Subtraction operation	$a - $b result is -10
*	Multiplication operation	$a * $b result is 200
/	Division operation	$b / $a result is 2
%	Modulus operation, remainder after division	$b % $a result is 0
**	Exponentiation	$a**$b result is 10 to the 20th power

Executing the above program produces the following output:

$a = 10 , $b = 20
$a + $b = 30
$a - $b = -10
$a * $b = 200
$a / $b = 0.5
$a % $b = 10
$a ** $b = 16

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Comparison Operators

In the following table examples, we set variable $a to 10 and $b to 20.

Operator	Description	Example
==	Checks whether the values of two operands are equal. If equal, the condition is true, otherwise false.	($a == $b) is false
!=	Checks whether the values of two operands are equal. If not equal, the condition is true, otherwise false.	($a != $b) is true.
<=>	Checks whether the values of two operands are equal. Returns -1 if the left number is less than the right number, 0 if equal, and 1 if the left number is greater than the right number.	($a <=> $b) returns -1.
>	Checks whether the value of the left operand is greater than the value of the right operand. If so, the condition is true, otherwise false.	($a > $b) returns false.
<	Checks whether the value of the left operand is less than the value of the right operand. If so, the condition is true, otherwise returns false.	($a < $b) returns true.
>=	Checks whether the value of the left operand is greater than or equal to the value of the right operand. If so, the condition is true, otherwise returns false.	($a >= $b) returns false.
<=	Checks whether the value of the left operand is less than or equal to the value of the right operand. If so, the condition is true, otherwise returns false.	($a <= $b) returns true.

Executing the above program produces the following output:

$a = 10 , $b = 20
$a == $b 结果 false
$a != $b 结果 true
$a <=> $b 返回 -1
$a > $b 结果 false
$a >= $b 结果 false
$a < $b 结果 true
$a <= $b 结果 true

In the following table examples, we set variable $a to "abc" and $b to "xyz", then use comparison operators to calculate the results.

Operator	Description	Example
lt	Checks whether the string on the left is less than the string on the right. If so, returns true, otherwise returns false.	($a lt $b) returns true.
gt	Checks whether the string on the left is greater than the string on the right. If so, returns true, otherwise returns false.	($a gt $b) returns false.
le	Checks whether the string on the left is less than or equal to the string on the right. If so, returns true, otherwise returns false.	($a le $b) returns true
ge	Checks whether the string on the left is greater than or equal to the string on the right. If so, returns true, otherwise returns false.	($a ge $b) returns false.
eq	Checks whether the string on the left is equal to the string on the right. If so, returns true, otherwise returns false.	($a eq $b) returns false.
ne	Checks whether the string on the left is not equal to the string on the right. If so, returns true, otherwise returns false.	($a ne $b) returns true
cmp	Returns 1 if the left string is greater than the right string, returns 0 if equal, and returns -1 if the left string is less than the right string.	($a cmp $b) returns -1.

Executing the above program produces the following output:

$a = abc ，$b = xyz
abc lt $b 返回 true
$a gt $b 返回 false
$a le $b 返回 true
$a ge $b 返回 false
$a ne $b 返回 true
$a cmp $b 返回 -1

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Assignment Operators

In the following table examples, we set variable $a to 10 and $b to 20.

Operator	Description	Example
=	Simple assignment operator, assigns the value of the right operand to the left operand	$c = $a + $b will assign the value of $a + $b to $c
+=	Add and assignment operator, assigns the result of adding the right operand to the left operand to the left operand	$c += $a is equivalent to $c = $c + $a
-=	Subtract and assignment operator, assigns the result of subtracting the right operand from the left operand to the left operand	$c -= $a is equivalent to $c = $c - $a
*=	Multiply and assignment operator, assigns the result of multiplying the right operand by the left operand to the left operand	$c *= $a is equivalent to $c = $c * $a
/=	Divide and assignment operator, assigns the result of dividing the left operand by the right operand to the left operand	$c /= $a is equivalent to $c = $c / $a
%=	Modulus and assignment operator, takes the modulus of the two operands and assigns it to the left operand	$c %= $a is equivalent to $c = $c % a
**=	Exponentiation and assignment operator, calculates the power of the two operands and assigns it to the left operand	$c **= $a is equivalent to $c = $c ** $a

Executing the above program produces the following output:

$a = 10 ，$b = 20
赋值后 $c = 30
$c = 40 ，运算语句 $c += $a
$c = 30 ，运算语句 $c -= $a
$c = 300 ，运算语句 $c *= $a
$c = 30 ，运算语句 $c /= $a
$c = 0 ，运算语句 $c %= $a
$a = 4 ， $c = 2
$c = 16 ，运算语句 $c **= $a

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Bitwise Operations

Bitwise operators act on bits and perform operations bit by bit.

Set $a = 60, $b = 13. Now represented in binary format, they are as follows:

$a = 0011 1100

$b = 0000 1101

-----------------

$a&$b = 0000 1100

$a|$b = 0011 1101

$a^$b = 0011 0001

~$a  = 1100 0011

The bitwise operators supported by Perl are shown in the following table:

Operator	Description	Example
&	If present in both operands, the binary AND operator copies a bit to the result.	($a & $b) will give 12, which is 0000 1100 in binary
|	If present in either operand, the binary OR operator copies a bit to the result.	($a | $b) will give 61, binary 0011 1101
^	Binary XOR operator copies a bit to the result if it exists in either operand but not in both.	($a ^ $b) will give 49, binary 0011 0001
~	The binary ones complement operator is a unary operator, having the effect of "flipping" bits, that is, 0 becomes 1, 1 becomes 0.	(~$a ) will give -61, binary 1100 0011, the ones complement form of a signed binary number.
<<	Binary left shift operator. The left operand's value is shifted left by the number of bits specified by the right operand.	$a << 2 will give 240, binary 1111 0000
>>	Binary right shift operator. The left operand's value is shifted right by the number of bits specified by the right operand.	$a >> 2 will give 15, binary 0000 1111

The output of the above program is:

$a = 60 , $b = 13
$a & $b = 12
$a | $b = 61
$a ^ $b = 49
~$a = -61
$a << 2 = 240
$a >> 2 = 15

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Logical Operators

Perl logical operators are shown in the following table.

In the table examples, we set variable $a to true, $b to false.

Operator	Description	Example
and	Logical AND operator. If both operands are true, the condition is true.	($a and $b) is false.
&&	C-style logical AND operator. If both operands are true, the condition is true.	($a && $b) is false.
or	Logical OR operator. If any one of the operands is non-zero, the condition is true.	($a or $b) is true.
||	C-style logical OR operator. If any one of the operands is non-zero, the condition is true.	($a || $b) is true.
not	Logical NOT operator. Used to reverse the logical state of the operand. If the condition is true, the logical NOT operator will make it false.	not($a and $b) is true.

The output of the above program is:

$a = true , $b = false
$a and $b = false
$a && $b = false
$a or $b = true
$a || $b = true
not($a)= 1

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Quote Operations

Perl quote operators are shown in the following table.

Operator	Description	Example
q{ }	Adds single quotes around a string	q{abcd} results in 'abcd'
qq{ }	Adds double quotes around a string	qq{abcd} results in "abcd"
qx{ }	Adds backticks around a string	qx{abcd} results in `abcd`

The output of the above program is:

q{a = $a} = a = $a
qq{a = $a} = a = 10
qx{date} = 2016年 6月10日 星期五 16时22分33秒 CST

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Other Operators

Besides the operators mentioned above, Perl also supports the following operators:

Operator	Description	Example
.	The dot (.) is used to concatenate two strings.	If $a="run", $b="oob", then $a.$b results in "example"
x	The x operator returns the string repeated a specified number of times.	('-' x 3) outputs ---.
..	.. is the range operator.	(2..5) outputs (2, 3, 4, 5)
++	Increment operator, increases the integer value by 1	$a =10, $a++ outputs 11
--	Decrement operator, decreases the integer value by 1	$a =10, $a-- outputs 9
->	The arrow is used to specify a method of a class	$obj->$a represents the $a method of object $obj.

The output of the above program is:

$a  = run ， $b = oob
$a . $b = example
"-" x 3 = ---
(2..5) = 2 3 4 5
$a  = 10 ， $b = 15
$a 执行 $a++ = 11
$b 执行 $b-- = 14

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Operator Precedence

The following table lists the operator precedence of the Perl language:

Operator	Associativity
++, --	None
-, ~, !	Right to left
**	Right to left
=~, !~	Left to right
*, /, %, x	Left to right
+, -, .	Left to right
<<, >>	Left to right
-e, -r,	None
<, <=, >, >=, lt, le, gt, ge	Left to right
==, !=, <=>, eq, ne, cmp	Left to right
&	Left to right
|, ^	Left to right
&&	Left to right
||	Left to right
..	Left to right
? and :	Right to left
=, +=, -=, *=,	Right to left
Other
,	Left to right
not	Left to right
and	Left to right
or, xor	Left to right

The output of the above program is:

$a  = 20, $b = 10, $c = 15 ，$d = 5
($a + $b) * $c / $d  = 90
(($a + $b) * $c) / $d  = 90
($a + $b) * ($c / $d )  = 90
$a + ($b * $c )/ $d  = 50

Other Extensions