Task — Valid tag

You are given a given a string caption for a video. Write a script to generate tag for the given string caption in three steps as mentioned below:

• Format as camelCase: Starting with a lower-case letter and capitalising the first letter of each subsequent word.
• Merge all words in the caption into a single string starting with
  a #.
• Sanitise the String: Strip out all characters that are not English letters (a-z or A-Z).
• Enforce Length: If the resulting string exceeds 100 characters, truncate it so it is exactly 100 characters long.

Examples

Example 1
Input: $caption = 'Cooking with 5 ingredients!'
Output: '#cookingWithIngredients'

Example 2
Input: $caption = 'the-last-of-the-mohicans'
Output: '#thelastofthemohicans'

Example 3
Input: $caption = '  extra spaces here'
Output: '#extraSpacesHere'

Example 4
Input: $caption = 'iPhone 15 Pro Max Review'
Output: '#iphoneProMaxReview'

Example 5
Input: $caption = 'Ultimate 24-Hour Challenge: Living in 
   a Smart Home controlled entirely by Artificial 
   Intelligence and Voice Commands in the year 2026!'
Output: '#ultimateHourChallengeLivingInASmartHomeControll
edEntirelyByArtificialIntelligenceAndVoiceCommandsIn'

Analysis

This is all achievable using simple regexes and built-in functions, but the order is important. Applying the steps in the order listed in the challenge doesn't quite achieve the desired output, but I think this does:

• lower-case the whole string
• remove anything that isn't a letter or a space
• remove initial spaces or initial non-letters
• replace space+letter with upper-case letter
• Remove any remaining spaces
• Prefix with '#'
• Truncate to max 100 chars

I have altered some of the supplied examples to test some edge cases.

Try it 

#!/usr/bin/perl

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

use v5.26;    # The Weekly Challenge - 2026-04-13
use utf8;     # Week 369 - task 1 - Valid tag
use warnings; # Peter Campbell Smith
binmode STDOUT, ':utf8';
use Encode;

valid_tag('Cooking with 5 ingredients!');
valid_tag('the-last-of-the-mohicans');
valid_tag('  extra  spaces  here  ');
valid_tag('!! iPhone 15 Pro Max Review !!');
valid_tag('Ultimate 24-Hour Challenge: Living in a Smart Home controlled entirely by Artificial Intelligence and Voice Commands in the year 2026!');

sub valid_tag {
    
    my ($text);
    
    # initialise
    $text = $_[0];
    say qq[\nInput:  '$text'];
    
    $text = lc($text);             # lower case all
    $text =~ s|[^a-z\s]||g;        # remove non-letters
    $text =~ s|^\s+||g;            # no initial spaces
    $text =~ s| ([a-z])|uc($1)|ge; # ucase space+letter
    $text =~ s|\s+||g;             # no spaces
    $text = substr('#' . $text, 0, 100); # prefix '#'
                                   # and max 100 chars  
    say qq[Output: '$text'];
}

last updated 2026-04-13 — 11 lines of code

Output

Input:  'Cooking with 5 ingredients!'
Output: '#cookingWithIngredients'

Input:  'the-last-of-the-mohicans'
Output: '#thelastofthemohicans'

Input:  '  extra  spaces  here  '
Output: '#extraSpacesHere'

Input:  '!! iPhone 15 Pro Max Review !!'
Output: '#iphoneProMaxReview'

Input:  'Ultimate 24-Hour Challenge: Living in a Smart 
   Home controlled entirely by Artificial Intelligence 
   and Voice Commands in the year 2026!'
Output: '#ultimateHourChallengeLivingInASmartHomeControll
edEntirelyByArtificialIntelligenceAndVoiceCommandsIn'