Perl Arrays & Lists

Arrays in Perl are ordered lists of scalars. They are prefixed with an @ symbol and can grow and shrink dynamically. Lists are ordered collections of scalars that are the data used to construct arrays.

Creating Arrays


# Simple array creation
@fruits = ("apple", "banana", "cherry");
@numbers = (1, 2, 3, 4, 5);
@mixed = ("hello", 42, 3.14, "world");

# Using qw (quote words) for cleaner syntax
@colors = qw(red green blue yellow);
@days = qw/Monday Tuesday Wednesday Thursday Friday/;

# Range operator
@digits = (0..9);
@letters = ('a'..'z');

Accessing Array Elements


# Accessing elements (0-based index)
print $fruits[0];  # "apple"
print $fruits[2];  # "cherry"

# Negative indices count from end
print $fruits[-1]; # "cherry" (last element)
print $fruits[-2]; # "banana" (second to last)

# Slices - accessing multiple elements
@first_two = @fruits[0,1];  # ("apple", "banana")
@every_other = @numbers[1,3]; # (2, 4)

Modifying Arrays


# Changing elements
$fruits[1] = "blueberry";  # Now ("apple", "blueberry", "cherry")

# Adding elements
push @fruits, "date";      # Add to end
unshift @fruits, "apricot"; # Add to beginning

# Removing elements
$last = pop @fruits;       # Remove from end
$first = shift @fruits;    # Remove from beginning

# Inserting elements
splice @numbers, 2, 0, (10, 11); # Insert 10,11 at position 2

# Deleting elements
splice @numbers, 1, 2;     # Remove 2 elements starting at position 1

Array Operations


# Array length
$count = @fruits;          # Scalar context gives length
$last_index = $#fruits;    # Index of last element

# Joining elements
$joined = join ", ", @fruits; # "apple, banana, cherry"

# Splitting strings into arrays
$line = "root:x:0:0:root:/root:/bin/bash";
@fields = split /:/, $line;

# Sorting
@sorted = sort @fruits;    # Alphabetical order
@reverse_sorted = reverse sort @fruits;

# Numeric sort
@numbers = (5, 2, 9, 1, 7);
@sorted_numbers = sort { $a <=> $b } @numbers;

Array Functions


# map - transform elements
@uppercased = map { uc } @fruits;  # ("APPLE", "BANANA", "CHERRY")

# grep - filter elements
@long_words = grep { length($_) > 5 } @words;

# List assignment
($first, $second, @rest) = @array;

# Array replication
@double = (@numbers, @numbers);

Special Array Variables


# Command line arguments
@ARGV = ("file1.txt", "file2.txt");

# Environment variables
%ENV;  # Hash containing environment variables

# Special arrays
@INC;  # Array of paths to search for modules
@ISA;  # Array of parent classes

Array Context


# Array in scalar context
$count = @array;  # Number of elements

# Array in list context
@copy = @array;   # Copies all elements

# Array slice
@first_three = @array[0..2];

# Array as stack
push @stack, $value;
$value = pop @stack;

# Array as queue
unshift @queue, $value;
$value = pop @queue;

Multidimensional Arrays


# Array of arrays
@matrix = (
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
);

# Accessing elements
$value = $matrix[1][2];  # 6

# Adding a row
push @matrix, [10, 11, 12];

Best Practices

Use push and pop instead of direct indexing when possible
Prefer foreach over C-style for loops for array iteration
Use array slices for multiple element access
Consider using references for complex data structures
Use exists to check for array indices when needed

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