Task — Text justifier

You are given a string and a width. Write a script to return the string that centers the text within that width using asterisks * as padding.

Examples

Example 1
Input: $str = 'Hi', $width = 5
Output: '*Hi**'
Text length = 2, Width = 5
Need 3 padding characters total
Left padding: 1 star, Right padding: 2 stars

Example 2
Input: $str = 'Code', $width = 10
Output: '***Code***'
Text length = 4, Width = 10
Need 6 padding characters total
Left padding: 3 stars, Right padding: 3 stars

Example 3
Input: $str = 'Hello', $width = 9
Output: '**Hello**'
Text length = 5, Width = 9
Need 4 padding characters total
Left padding: 2 stars, Right padding: 2 stars

Example 4
Input: $str = 'Perl', $width = 4
Output: 'Perl'
No padding needed

Example 5
Input: $str = 'A', $width = 7
Output: '***A***'
Text length = 1, Width = 7
Need 6 padding characters total
Left padding: 3 stars, Right padding: 3 stars

Example 6
Input: $str = '', $width = 5
Output: '*****'
Text length = 0, Width = 5
Entire output is padding

Analysis

This is not a hard challenge, and as in many previous ones it can probably be done with a single rather impenetrable regular expression. I'll leave that for others to do.

I took the simple approach of calculating the number of asterisks required:

$asterisks = $width - length($string);

and then concatenating

• int($asterisks / 2) asterisks
• the input string
• ($asterisks - int($asterisks / 2)) asterisks.

That copes with all the edge cases such as an empty string, a zero $width with an empty string, and a string with just one fewer characters than $width.

And lastly I retun an error meesage if $string is longer than $width.

Try it 

#!/usr/bin/perl

# Blog: http://ccgi.campbellsmiths.force9.co.uk/challenge

use v5.26;    # The Weekly Challenge - 2026-02-09
use utf8;     # Week 360 - task 1 - Text justifier
use warnings; # Peter Campbell Smith
binmode STDOUT, ':utf8';
use Encode;

text_justifier('Code', 10);
text_justifier('Toad', 11);
text_justifier('Road', 4);
text_justifier('Mode', 20);
text_justifier('Node', 21);
text_justifier('Bode', 5);
text_justifier('', 1);
text_justifier('', 0);

sub text_justifier {
    
    my ($string, $width, $length, $asterisks, $left, $output);
    
    # initialise
    ($string, $width) = @_;
    say qq[\nInput:  \$string = '$string', \$width = $width];
    
    # how many asterisks?
    $asterisks = $width - length($string);
    
    # we can do it
    if ($asterisks >= 0) {
        $left = int($asterisks / 2);
        say qq[Output: ] . ('*' x $left) . $string . ('*' x ($asterisks - $left));
        
    # but not if the string won't fit
    } else {
        say qq[Output: Error: string is longer than width];
    }
}

Output

Input:  $string = 'Code', $width = 10
Output: ***Code***

Input:  $string = 'Toad', $width = 11
Output: ***Toad****

Input:  $string = 'Road', $width = 4
Output: Road

Input:  $string = 'Mode', $width = 20
Output: ********Mode********

Input:  $string = 'Node', $width = 21
Output: ********Node*********

Input:  $string = 'Bode', $width = 5
Output: Bode*

Input:  $string = '', $width = 1
Output: *

Input:  $string = '', $width = 0
Output: