Capital detection

You are given a string with alphabetic characters only: A..Z and a..z.

Write a script to find out if the usage of capitals is appropriate if it satisfies at least one of the following rules:

1. Only first letter is capital and all others are small.
2. Every letter is small.
3. Every letter is capital.

Examples

Example 1
Input: $s = 'Perl'
Output: 1

Example 2
Input: $s = 'TPF'
Output: 1

Example 3
Input: $s = 'PyThon'
Output: 0

Example 4
Input: $s = 'raku'
Output: 1

Analysis

Generally I steer clear of hard-to-follow one-liners, but this one is fairly simple:

$test =~ m/^[A-Z]?([a-z]*|[A-Z]*)$/ ? 1 : 0;

In words, the string follows the rule if:

• it starts with zero or one capital letter, and
• it continues with either zero or more capital letters, or zero or more lower case letters.

Well crafted breakdown of the task makes it so easy to follow. Keep it up great work.

Try it 

Try running the script with any input:

Your $string =

example: Challenge

⤡

#!/usr/bin/perl

# Peter Campbell Smith - 2022-11-07
# PWC 190 task 1

use v5.28;
use utf8;
use warnings;
binmode(STDOUT, ':utf8');

my (@tests, $test);

@tests = qw[Perl PWC PyThon raku Byron ShakesSpeare miltoN KEATS 123 6-fold Hello! a A];

# loop over tests
 while ($test = shift @tests) {
     say qq[\nInput:  $test\nOutput: ] . ($test =~ m/^[A-Z]?([a-z]*|[A-Z]*)$/ ? 1 : 0);
}

8 lines of code

Output from script

Input:  Perl
Output: 1

Input:  PWC
Output: 1

Input:  PyThon
Output: 0

Input:  raku
Output: 1

Input:  Byron
Output: 1

Input:  ShakesSpeare
Output: 0

Input:  miltoN
Output: 0

Input:  KEATS
Output: 1

Input:  123
Output: 0

Input:  6-fold
Output: 0

Input:  Hello!
Output: 0

Input:  a
Output: 1

Input:  A
Output: 1