Perl Operators

Arithmetic Operators

Basic Arithmetic Operators

my $a = 10;
my $b = 3;

print $a + $b;   # Addition: 13
print $a - $b;   # Subtraction: 7
print $a * $b;   # Multiplication: 30
print $a / $b;   # Division: 3.33333333333333
print $a % $b;   # Modulus: 1
print $a ** $b;  # Exponentiation: 1000

Arithmetic Assignment Operators

my $num = 10;

$num += 5;   # $num = $num + 5   Result: 15
$num -= 3;   # $num = $num - 3   Result: 12
$num *= 2;   # $num = $num * 2   Result: 24
$num /= 4;   # $num = $num / 4   Result: 6
$num %= 4;   # $num = $num % 4   Result: 2
$num **= 3;  # $num = $num ** 3  Result: 8

Increment and Decrement

my $num = 5;

$num++;      # Increment: 6
$num--;      # Decrement: 5

# Difference between prefix and postfix
my $a = 5;
my $b = ++$a;  # Increment first, then assign: $a=6, $b=6

my $c = 5;
my $d = $c++;  # Assign first, then increment: $c=6, $d=5

String Operators

String Concatenation

my $str1 = "Hello";
my $str2 = "World";
my $combined = $str1 . " " . $str2;  # "Hello World"

String Repetition

my $line = "-" x 20;  # "--------------------"
my $beep = "a" x 5;   # "aaaaa"

String Comparison Operators

my $str1 = "apple";
my $str2 = "banana";

print $str1 eq $str2;  # Equal: 0 (false)
print $str1 ne $str2;  # Not equal: 1 (true)
print $str1 lt $str2;  # Less than: 1 (true)
print $str1 gt $str2;  # Greater than: 0 (false)
print $str1 le $str2;  # Less or equal: 1 (true)
print $str1 ge $str2;  # Greater or equal: 0 (false)

# Using cmp returns -1, 0, or 1
print $str1 cmp $str2;  # -1 (less than)

Comparison Operators

Numeric Comparison

my $a = 10;
my $b = 20;

print $a == $b;   # Equal: 0 (false)
print $a != $b;   # Not equal: 1 (true)
print $a < $b;    # Less than: 1 (true)
print $a > $b;    # Greater than: 0 (false)
print $a <= $b;   # Less or equal: 1 (true)
print $a >= $b;   # Greater or equal: 0 (false)

# Using <=> returns -1, 0, or 1
print $a <=> $b;   # -1 (less than)

Comparison Operators Summary

Numeric	String	Description
==	eq	Equal
!=	ne	Not equal
<	lt	Less than
>	gt	Greater than
<=	le	Less or equal
>=	ge	Greater or equal
<=>	cmp	Compare returns -1/0/1

Logical Operators

Basic Logical Operators

my $a = 1;
my $b = 0;

print $a && $b;   # Logical AND: 0
print $a || $b;   # Logical OR: 1
print !$a;         # Logical NOT: 0

Low-precedence Logical Operators

my $a = 1;
my $b = 0;

print $a and $b;   # Logical AND: 0
print $a or $b;    # Logical OR: 1
print not $a;      # Logical NOT: 0

Ternary Operator

my $age = 18;
my $status = $age >= 18 ? "adult" : "minor";
print $status;  # "adult"

Short-circuit Evaluation

# Logical AND: if first is false, second not evaluated
my $x = 0;
my $y = 10;
my $result = $x && ($y = 20);  # $y won't be modified

# Logical OR: if first is true, second not evaluated
my $a = 1;
my $b = 10;
my $result2 = $a || ($b = 20);  # $b won't be modified

# Defined-or operator
my $value = $input // "default";

Bitwise Operators

my $a = 5;   # Binary: 101
my $b = 3;   # Binary: 011

print $a & $b;   # Bitwise AND: 1 (001)
print $a | $b;   # Bitwise OR: 7 (111)
print $a ^ $b;   # Bitwise XOR: 6 (110)
print ~$a;        # Bitwise NOT: -6
print $a << 1;    # Left shift: 10 (1010)
print $a >> 1;    # Right shift: 2 (010)

Assignment Operators

my $a = 10;      # Assignment

my $b = $a;      # Copy
$a = $b = 5;     # Chained assignment

# Multiple value assignment
my ($x, $y, $z) = (1, 2, 3);

Comma Operator

# In scalar context returns last value
my $result = (1, 2, 3);  # $result = 3

# In list context returns entire list
my @array = (1, 2, 3);   # @array = (1, 2, 3)

# Using in for loops
for (my $i = 0, my $j = 10; $i < 10; $i++, $j--) {
    print "$i, $j\n";
}

Range Operator

# Numeric range
my @nums = 1..10;  # (1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

# Character range
my @chars = 'a'..'z';  # ('a', 'b', ..., 'z')

# Conditional range
while (<>) {
    print if /start/../end/;  # Print lines between /start/ and /end/
}

Advanced String Operators

String Concatenation and Assignment

my $str = "Hello";
$str .= " World";  # $str = "Hello World"

Smart Matching (String)

use v5.10;

my $name = "Alice";

if ($name ~~ qr/^A/) {
    print "Starts with A\n";
}

File Test Operators

my $file = "test.txt";

print -e $file;   # File exists
print -f $file;   # Is regular file
print -d $file;   # Is directory
print -r $file;   # Is readable
print -w $file;   # Is writable
print -x $file;   # Is executable
print -s $file;   # File size (bytes)
print -z $file;   # File is empty

Regex Operators

my $text = "Hello World";

# Match
if ($text =~ /World/) {
    print "Found!\n";
}

# No match
if ($text !~ /Python/) {
    print "Not found!\n";
}

# Substitution
$text =~ s/World/Perl/;  # "Hello Perl"

# Global substitution
$text =~ s/l/x/g;  # "Hexxo Perx"

Reference Operators

# Backslash creates reference
my $scalar = 42;
my $scalar_ref = \$scalar;

my @array = (1, 2, 3);
my $array_ref = \@array;

my %hash = (key => "value");
my $hash_ref = \%hash;

# Square brackets create anonymous array
my $anon_array = [1, 2, 3];

# Curly braces create anonymous hash
my $anon_hash = {name => "Alice"};

Dereference Operators

my $array_ref = [1, 2, 3];
my @array = @$array_ref;     # Dereference to array
my $first = $array_ref->[0];  # Arrow operator

my $hash_ref = {name => "Alice"};
my %hash = %$hash_ref;       # Dereference to hash
my $name = $hash_ref->{name}; # Arrow operator

Operator Precedence

Precedence from High to Low

1. Terms and list operators (left)
2. ->
3. ++ -- (increment/decrement)
4. ** (exponentiation)
5. ! ~ \ + - (logical not, bitwise not, reference, unary plus/minus)
6. =~ !~ (matching)
7. * / % x (multiply, divide, modulus, repetition)
8. + - . (add, subtract, concatenation)
9. << >> (shift)
10. Named unary operators
11. < <= > >= lt le gt ge (comparison)
12. == != <=> eq ne cmp (equality comparison)
13. & (bitwise AND)
14. | ^ (bitwise OR, XOR)
15. && (logical AND)
16. || // (logical OR, defined-or)
17. .. ... (range)
18. ?: (ternary operator)
19. = += -= *= etc. (assignment)
20. , => (comma, fat arrow)
21. Logical operators (right)
22. and or xor (low-precedence logical)

Using Parentheses for Clarity

# Use parentheses when precedence is unclear
my $result = ($a + $b) * $c;
my $condition = ($x > 0) and ($y < 10);

Practice Examples

Example 1: Calculator

#!/usr/bin/perl
use strict;
use warnings;

print "Enter first number: ";
chomp(my $num1 = <STDIN>);

print "Enter second number: ";
chomp(my $num2 = <STDIN>);

printf "Addition: %d + %d = %d\n", $num1, $num2, $num1 + $num2;
printf "Subtraction: %d - %d = %d\n", $num1, $num2, $num1 - $num2;
printf "Multiplication: %d * %d = %d\n", $num1, $num2, $num1 * $num2;
printf "Division: %d / %d = %.2f\n", $num1, $num2, $num1 / $num2;
printf "Modulus: %d %% %d = %d\n", $num1, $num2, $num1 % $num2;
printf "Power: %d ** %d = %d\n", $num1, $num2, $num1 ** $num2;

Example 2: String Operations

#!/usr/bin/perl
use strict;
use warnings;

my $str1 = "Hello";
my $str2 = "World";

my $combined = $str1 . " " . $str2;
print "Concatenation: $combined\n";

my $repeated = $str1 x 3;
print "Repetition: $repeated\n";

print "Length: " . length($combined) . "\n";

if ($str1 lt $str2) {
    print "'$str1' comes before '$str2' in dictionary order\n";
}

Example 3: Logical Decisions

#!/usr/bin/perl
use strict;
use warnings;

my $age = 25;
my $has_license = 1;
my $has_car = 0;

my $can_drive = $age >= 18 && $has_license;
print "Can drive: " . ($can_drive ? "Yes" : "No") . "\n";

my $can_travel = $has_license || $has_car;
print "Can travel: " . ($can_travel ? "Yes" : "No") . "\n";

my $status = $age >= 18 ? "Adult" : "Minor";
print "Status: $status\n";

Summary

In this chapter, we learned Perl operators:

1. ✅ Arithmetic operators
2. ✅ String operators
3. ✅ Comparison operators
4. ✅ Logical operators
5. ✅ Bitwise operators
6. ✅ Assignment operators
7. ✅ File test operators
8. ✅ Regex operators
9. ✅ Operator precedence

Next, we will learn Perl Conditional Statements.