How to copy an array in Perl?

In Perl, copying an array means creating a new array that contains the same elements as the original array, but is a separate data structure. This is important because simply assigning one array to another does not create a distinct copy — it makes the new array a reference to the same underlying data. To properly copy (or clone) an array, you need to create a new array that contains the elements of the original.

Copying Arrays in Perl: Basic Concept

Arrays in Perl are identified by the @ sigil. To copy an array, you can use the feature that extracting an array in list context returns all its elements. Then assigning this list to a new array makes a full copy.

Here is the simplest way to copy an array:

my @original = (1, 2, 3, 4);
my @copy = @original;  # Copy by simple assignment (list context)

Now, @copy holds the same elements as @original, but the two arrays are independent. Changing one will not affect the other.

Complete Runnable Example

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

# Original array
my @original = ('apple', 'banana', 'cherry');

# Copy the array
my @copy = @original;

# Modify the copy
$copy[0] = 'apricot';

# Print both arrays to show they are independent
print "Original: @original\n";
print "Copy: @copy\n";

When you run this script, the output will be:

Original: apple banana cherry
Copy: apricot banana cherry

This shows that the copy is a separate array and modifications to @copy don’t affect @original.

Perl Concepts Highlighted

• Sigils: Arrays use @, array elements use $ because they are scalars. For example, $array[0] accesses one element.
• Context: Assigning an array to another array happens in list context, so the full list of elements is copied.
• TMTOWTDI (There’s more than one way to do it): Besides simple assignment, other ways exist (like using array slices, or @copy = @original[0..$#original]), but simple assignment is the most straightforward.

Common Pitfalls

• Assigning array references (e.g., $copy = \@original) does not copy the array, only creates a new reference to the same data.
• Copying multidimensional arrays requires deep cloning (copying nested arrays), which is more advanced and may require modules like Storable or recursion.
• Remember to use strict and warnings to catch potential issues.

In summary, copying a Perl array is most easily done by assigning the original array to a new array variable, which makes a shallow copy of all elements. This works perfectly for simple lists of scalars.