Perl Operators



Before trying to organize the Perl operators, let's speak a litle about what we mean by operator in a programming language.

The operators work with numbers and strings and manipulate data objects called operands. We found the operators in expressions which we need to evaluate.

On the other side, we use Perl operators in a certain context. We have two types of contexts: the scalar context which is invoked when Perl is expected to return a single value (like the addition of two numbers) and the list context when Perl is expected to return two or more values.

The great majority of the Perl operators work in scalar context, if not we will specify.

Also note that you must be aware of the Perl operators precedence, if you are not sure, it is better to use the brackets.



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1. NUMERIC PERL OPERATORS


   1.1. ARITHMETIC PERL OPERATORS


In the table below you see the Perl operators used in arithmetic operations.

Symbol Name Definition
+ addition It's a binary operator that returns the sum of two operands.

Example:

 $v1 = 12;
 $v2 = 5;
 $v = $v1+$v2;
 print "$v (expected 17)\n";

- subtraction It's a binary operator that returns the difference of two operands.

Example:

 $v1 = 12;
 $v2 = 5;
 $v = $v1-$v2;
 print "$v (expected 7)\n";

- negation I's a unary operator that performs arithmetic negation.

Example:

 $v1 = 12; 
 $v2 = -$v1;
 print "$v2 (expected -12)\n"; 

* multiplication It's a binary operator that multiplies two operands.

Example:

 $v1 = 12; 
 $v2 = 5;
 $v = $v1 * $v2;
 print "$v (expected 60)\n"; 

/ division It's a binary operator that divides left value by right value.

Example:

 $v1 = 12; 
 $v2 = 5;
 $v = $v1 / $v2;
 print "$v (expected 2.4)\n"; 

** exponentiation It's a binary operator that raises the left value to the power of the right value.

Example:

 $v1 = 12; 
 $v2 = 2;
 $v = $v1 ** $v2;
 print "$v (expected 144)\n";

% modulus It's a binary operator that returns the remainder of dividing left value by right value.

Example:

 $v1 = 12;
 $v2 = 5;
 $v = $v1 % $v2;
 print "$v (expected 2)\n";

++ autoincrement If you place this unary operator before/after a variable, the variable will be incremented before/after returning the value.

Example:

 $v1 = 10; 
 $v2 = ++$v1;
 print "$v1 $v2(expected 11 11)\n";
 $v1 = 10; 
 $v2 = $v1++;
 print "$v1 $v2(expected 11 10)\n";

-- autodecrement If you place this unary operator before/after a variable, the variable will be decremented before/after returning the value.

Example:

 $v1 = 10;
 $v2 = --$v1;
 print "$v1 $v2(expected 9 9)\n"; 
 $v1 = 10;
 $v2 = $v1--;
 print "$v1 $v2(expected 9 10)\n";



    1.2. NUMERIC RELATIONAL PERL OPERATORS


The numeric relational Perl operators compare two numbers and determine the validity of a relationship.

Symbol Name Definition
< less then The "less then" operator indicates if the value of the left operand is less than the value of the right one.

Example:
 ($v1, $v2) = (5, 7);
 if($v1 < $v2){
   print "OK (expected)\n";
 }
<= less than or equal to The "less than or equal to" operator indicates if the value of the left operand is less than or equal to the value of the right one.

Example:
  ($v1, $v2) = (5, 5);
  if($v1 <= $v2){
    print "OK (expected)\n";
  }
> greater than The "greater than" operator indicates if the value of the left operand is greater than the value of the right one.

Example:
 ($v1, $v2) = (5, 7);
 if($v2 > $v1){
   print "OK (expected)\n";
 }
>= greater than or equal to The "greater than or equal to" operator indicates if the value of the left operand is greater than or equal to the value of the right one.

Example:
 ($v1, $v2) = (5, 5);
 if($v2 >= $v1){
   print "OK (expected)\n";
 }
== equal The "equal" operator returns true if the left operand is equal to the right one.

Example:
 ($v1, $v2) = (5, 5);
 if($v1 == $v2){
   print "OK (expected)\n";
 }
!= not equal to The "not equal to" operator returns true if the left operand is not equal to the right one.

Example:
 ($v1, $v2) = (5, 7);
 if($v1 != $v2){
   print "OK (expected)\n";
}
<=> numeric comparison This binary operator returns -1, 0, or 1 if the left operand is less than, equal to or greater than the right one.

Example:
 ($v1, $v2) = (5, 7);
 $v = $v1 <=> $v2;
 print "$v\n"; # displays -1;

    1.3. NUMERIC LOGICAL PERL OPERATORS


The numeric logical Perl operators are generally derived from boolean algebra and they are mainly used to control program flow, finding them as part of an if, a while or some other control statement. See in the table below the logical numerical Perl operators.

Symbol Name Definition
! negation This unary operator evaluates an operand and return true if the operand has the false value (0) and false otherwise.

Example:
 $v1 = !25;
 $v2 = !0;
 print "v1=$v1,v2=$v2\n"; # displays v1=,v2=1
not not It has the same meaning as the "!" operator, described above.
and, && and The "and" operator returns the logical conjunction of two operands.

Example:
 ($v1, $v2) = (5, 7);
 if($v1 == 5 && $v2 == 7) {
   print "OK (expected)\n";
 }
or, || or The "or" operator returns the logical disjunction of two operands.

Example:
 ($v1, $v2) = (5, 7);
 if($v1 == 5 || $v2 == 0) {
   print "OK (expected)\n";
 }

xor exclusive or The "exclusive or" operator returns the logical exclusive-or of two operands (the result is true if either but not both of the operands is true).

Example:
 ($v1, $v2) = (5, 7);
 print ($v1==5 xor $v2==3); # displays 1
 print ($v1==5 xor $v2==7); # displays
? conditional operator This ternary operator is like the symbolic if ... then ... else clause from the C language. It returns the second operand if the leftmost operand is true and the third operand otherwise.

Example:

 $v = (2 == 2) ? "Equal\n" : "Not equal\n";
 print $v; # displays Equal


    1.4. NUMERIC BITWISE PERL OPERATORS


Numeric bitwise Perl operators are similar to the logical operators, but they work on the binary representation of data. They are used to change individual bits in an operand. Please note that both operands associated with bitwise operators are integers.

Symbol Name Definition
<< shift left The "shift left" << operator is a binary operator that shifts the bits to the left. Its first operand specifies the integer value to be shifted meanwhile the second one specifies the number of position that the bits in the value will be shifted. The rightmost bits of the integer value will be assigned with 0 and the leftmost bits will be discarded.

Example:

 $v = 25 << 3;
 print "$v (expected 200)\n";
>> shift right The "shift right" >> operator is a binary operator that shifts the bits to the right. Its first operand specifies the integer value to be shifted meanwhile the second one specifies the number of position that the bits in the value will be shifted. The leftmost bits of the integer value will be assigned with 0 and the rightmost bits will be discarded.

Example:
 $v = 32 >> 3;
 print "$v (expected 4)\n";
& and The "and" operator sets a bit to 1 if both of the corresponding bits in its operands are 1, and 0 otherwise.

Example:
 $v = 32 & 16;
 print "$v (expected 0)\n";
| or The "or" operator sets a bit to 0 if both of the corresponding bits in its operands are 0, and 1 otherwise.

Example:
 $v = 32 | 16;
 print "$v (expected 48)\n";
^ exclusive or The "exclusive or" operator sets a bit to 1 if the corresponding bits in its operands are different, and 0 otherwise.

Example:
 $v = 3 ^ 9;
 print "$v (expected 10)\n";
~ not The unary "not" operator inverts each bit in the operand, changing all the ones to zeros and zeros to ones.

Example:
 $v = ~1024;

    1.5. OTHER NUMERIC PERL OPERATORS


See in the table below other numeric Perl operators:

Symbol Name Definition
, comma In scalar context this binary operator evaluates its left argument, discards this value, then evaluates its right argument and returns that value. In a list context, it's just a separator and inserts both its arguments into the list.

Example (in scalar context):
 $v1 = 2; $v2 = 4; $v3 = $v1 == $v2;
 $v = ($v3, 5 == 5);
 print(" $v3(expected )\n");
 print(" $v(expected 1)\n");
=> comma It has the same function like the comma operator described above.
.. Range operator In scalar context, this operator returns false as long as its left operand is false. When the left operand becomes true, the range operator returns true until the right operator remains true, after which it becomes false again. In a list context, this operator will return an array with contiguous sequences of items, beginning with the left operand value and ending with the right operand value (the items can be characters or numbers).

Example (in a list context):
 print ('a'..'zz');  
 print ('1'..'10');

    1.6. NUMERIC ASSIGNMENT PERL OPERATORS


Numeric assignment Perl operators perform some type of numeric operation and then assign the value to the existing variable.

Symbol Name Definition
= assignment This is the ordinary assignment operator. In a scalar context, it assigns the right operand's value to the left operand. In a list context, it assigns multiple values to the left array operand if the right operand is a list.

Example:
 $v = 15;  
 print $v, "\n";   # displays 15
 @array = (10, 20, 30);
 print "@array\n"; # displays 10 20 30
+= addition It adds the right operand's value to the left operand.

Example:
 $v = 10;
 $v += 15;
 print "$v (expected 25)\n";
-= subtraction It subtracts the right operand from the left operand.
 $v = 25;
 $v -= 15;
 print "$v (expected 10)\n";
*= multiplication It multiplies the left operand's value by the right operand's value.

Example:
 $v = 10; 
 $v *= 15;
 print "$v (expected 150)\n";
/= division It divides the left operand's value by the right operand's value.

Example:
 $v = 150;
 $v /= 15;
 print "$v (expected 10)\n";
**= exponentiation It raises the left operand's value to the power of the right operand's value.

Example:
 $v = 12;
 $v **= 2;
 print "$v (expected 144)\n";
%= modulus It divides the left operand value by the right operand value and assigns the remainder to the left operand.

Example:
 $v = 12;
 $v %= 5;
 print "$v (expected 2)\n"; 
 
&&= logical and It's a combination between the logical "&&" and the assignment operators.

Example:
 $v = 1;
 $v &&= 7 == 7;
 print "$v (expected 1)\n";
||= logical or It's a combination between the logical "||" and the assignment operators.

Example:
 $v = 0;
 $v ||= 7 == 7;
 print "$v (expected 1)\n";
 
<<= bitwise shift left It's a bitwise left shift assign.

Example:
 $v = 25;
 $v <<= 3;
 print "$v (expected 200)\n";
>>= bitwise shift right It's a bitwise right shift assign.

Example:
 $v = 32;
 $v >>= 3;
 print "$v (expected 4)\n";
&= bitwise and It's a bitwise AND assign.

Example:
 $v = 32;
 $v &= 16;
 print "$v (expected 0)\n";
|= bitwise or It's a bitwise OR assign.

Example:
 $v = 32;
 $v |= 16;
 print "$v (expected 48)\n";
^= bitwise exclusive or It's a bitwise XOR assign.

Example:
 $v = 3;
 $v ^= 9;
 print "$v (expected 10)\n";


2. STRING PERL OPERATORS


    2.1.STRING RELATIONAL PERL OPERATORS


The string relational Perl operators compare two strings and determine the validity of a relationship.

Symbol Name Definition
lt less than It returns true if the left operand is stringwise less then the right one.

Example:
 ($v1, $v2) = ("abc", "abz");
 if($v1 lt $v2){
   print ("$v1 is less than $v2\n");
 }
le less than or equal to It returns true if the left operand is stringwise less then or equal to the right one.

Example:
 ($v1, $v2) = ("abc", "abc");
 if($v1 le $v2){
   print("$v1 is less than or equal to $v2");
   print "\n";
 }
gt greater than It returns true if the left operand is stringwise greater then the right one.

Example:
 ($v1, $v2) = ("abc", "abz");
 if($v2 gt $v1){
   print ("$v2 is greater than $v1\n");
 }
ge greater than or equal to It returns true if the left operand is stringwise greater then or equal to the right one.

Example:
 ($v1, $v2) = ("abc", "abc");
 if($v1 ge $v2){
   print("$v1 is greater than or equal to $v2");
   print "\n";
 }
eq equality It returns true if the left operand is stringwise equal to the right one.

Example:
 ($v1, $v2) = ("abc", "abc");
 if($v1 eq $v2){
   print ("$v1 is equal to $v2\n");
}
ne not equal to It returns true if the left operand is stringwise not equal to the right one.

Example:
 ($v1, $v2) = ("abc", "ab1");
 if($v1 ne $v2){
   print ("$v1 is not equal to $v2\n");
 }
cmp comparison It returns -1, 0, or 1 if the left operand is stringwise less than, equal to or greater than the right one.

Example:
 ($v1, $v2) = ("am", "ak");
 $v = $v1 cmp $v2;
 print ("$v(expected 1)\n");

    2.2. STRING LOGICAL PERL OPERATORS


The string logical Perl operators are generally derived from boolean algebra and they are mainly used to control program flow, finding them as part of an if, a while or some other control statement. See in the table below the logical string Perl operators.

Symbol Name Definition
! not It returns true if the operand is a null string or an undefined value and false otherwise.

Example:
 $v1 = !'some string here';  
 $v2 = !'';
The $v1 variable will return false and the $v2 variable will return true.
not not The same meaning as above, but it is a lower-precedence version.
&& and This operator is used to determine if both operands are true.

Example:
 ($v1, $v2) = ('abc', 'abzu');
 $v = $v1 == 'abc' && $v2 == 'abzu';
 print "$v (expected 1)";
and and Same as above.
|| or This operator is used to determine if either of the operands is true.

Example:
 ($v1, $v2) = ('hello', 'good');
 $v = $v1 == 'hello' || $v2 == 'hello'; 
 print "$v (expected 1)";
or or Same as above.
xor exclusive or It returns true if either but not both of the operands is true.

Example:
 ($v1, $v2) = ('hello', 'good');
 $v = $v1 == 'hello' xor $v2 == 'world';
 print "$v (expected 1)";
? conditional operator This is a ternary operator and it works like an if ... then ... else clause from the C language. If the left operand is true, it will return the central operand, otherwise the right operand.

Example:
 $v = ("abc" eq "abd") ? "It's equal.\n" : 
       "It's not equal. (expected)\n";  
 print $v;


    2.3. OTHER STRING PERL OPERATORS


See in the table below other string Perl operators:

Symbol Name Definition
, comma In a scalar context, the comma operator evaluates each element from left to right and returns the value of the rightmost element. In a list context, the comma operator separates the elements of a literal list.

Example:
 # scalar context
 $colors = ('blue', 'red', 'yellow');  
 print "$colors (expected yellow)\n";
 # list context
 @colors = ('blue', 'red', 'yellow'); 
 print "@colors[1] (expected red)\n";
=> comma This operator is a special type of comma, for example ('dog', 'cat') is similar to (dog => 'cat'). Or it can be used to separate key/value pairs in a hash structure: %petColors = (dog => 'brown', cat => 'white');

- negation If the string operand begins with a plus or minus sign, the string negation operator returns a string with the opposite sign.

Example:
 $v = "-abcd";
 print (-$v, "(expected +abcd)\n"); 
. concatenation This operator joins two or more strings like in the example below.

Example:
 $v = "Hello" . " World" . "!"; 
 print $v, " (expected Hello World!)\n"; 
.. range operator The range operator, in a list context, produces the range of values from the left value through the right value in increments of 1.

Example:
 @v = ('ab' .. 'ae'); 
 print @v, " (expected abacadae)\n";
x repetition The repetition operator returns the first operand (which is a string) repeated by the number of times specified by the second operand (which is an integer).

Example:
 @v = 'ab' x 3;
 print @v, " (expected ababab)\n"; 

    2.4. STRING ASSIGNMENT PERL OPERATORS


String assignment Perl operators perform some type of string operation and then assign the value to the existing variable.

Symbol Name Definition
= assignment This is the ordinary assignment operator.

Example:
 $v = 'Hello World!';
 print $v, " (expected Hello World!)\n";
&&= logical and It's a combination between the logical "&&" and the assignment operators.

Example:
 $v = 1;
 $v &&= 'abc' eq 'abc';
 print $v, " (expected 1)\n";
||= logical or It's a combination between the logical "||" and the assignment operators.

Example:
 $v = 0;
 $v ||= 'abc' eq 'abc'; 
 print $v, " (expected 1)\n"; 
.= concatenation It's a combination between the concatenation "." and the assignment operators.

Example:
 $v = "Hello ";
 $v .= 'World!'; 
 print $v, " (expected Hello World!)\n";
x= repetition It's a repetition assignment operator.

Example:
 $v = "true ";
 $v x= 2;
 print $v, " (expected true true )\n"; 

3. SPECIAL PERL OPERATORS


See in the table below the special Perl operators:

Symbol Name Definition
\ reference We call reference the scalar value that contains a memory address. In order to reference a variable, we use the operator. Look at the below snippet code to see how to use it.

Example:
 $v="Hello World!";
 $ref_v=\$v;
 print $$ref_v, " (expected Hello World!)\n";
-> dereference The dereference operator was used for the first time in the Perl 5 language. This operator let us to access and manipulate the elements of an array, hash, object of a class data structure. If you use the reference operator to reference a scalar variable, before you use it you must dereference the reference variable.

Example:
 @v = ('black', 'white', 'blue', 'orange');
 $vRef = \@v; # the reference variable 
 print $v[1], " (expected white)\n"; 
 $vRef->[1] = 'red'; # dereference before use 
 print $v[1], " (expected red)\n"; 
=~ pattern binding This binary operator binds a string expression to a pattern match. The string which is intend to bind is put on the left meanwhile the operator itself is put on the right. We use the pattern binding operator in the case we have a string which is not stored in the $_ variable and we need to perform some matches or substitutions of that string.

Example:
 $v = "black and white";
 if($v =~ m/white/) {
   print "Yes (expected)\n"; 
 }
 $v =~ s/black and white/red/;
 print $v, " (expected red)\n";
!~ pattern binding (not) This operator is similar the operator above, but the return value is negated logically.

Example:
 $v = "black and white";
 if($v =! m/yellow/) {
   print "Yes (expected)\n";
 }


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Table of Contents:

A Perl Script
Install Perl
Running Perl
Perl Data Types
Perl Variables
Perl Operators (more)
Perl Lists
Perl Arrays
    Array Size
    Array Length
Perl Hashes
Perl Statements
    Perl if
    Perl unless
    Perl switch
    Perl while
    Perl do-while
    Perl until
    Perl do-until
    Perl for
    Perl foreach
Built-in Perl Functions
    Functions by Category
        String Functions
        Regular Expressions and Pattern Matching
        List Functions
        Array Functions
        Hash Functions
        Miscellaneous Functions
    Functions in alphabetical order
        chomp
        chop
        chr
        crypt
        defined
        delete
        each
        exists
        grep
        hex
        index
        join
        keys
        lc
        lcfirst
        length
        map
        oct
        ord
        pack
        pop
        push
        q
        qq
        qw
        reverse
        rindex
        scalar
        shift
        sort
        splice
        split
        sprintf
        substr
        tr
        uc
        ucfirst
        undef
        unpack
        unshift
        values

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