============================================================
 STRING MANIPULATION TOOLKIT - Demo Run
============================================================

--- reverse_string ---
  reverse_string('hello') = 'olleh'
  reverse_string('Python') = 'nohtyP'
  reverse_string('') = ''

--- is_palindrome ---
  is_palindrome('racecar') = True
  is_palindrome('A man a plan a canal Panama') = True
  is_palindrome('hello') = False
  is_palindrome('') = True

--- count_vowels_consonants ---
  'Hello World': vowels=3, consonants=7
  '   ': vowels=0, consonants=0
  'Python Programming': vowels=4, consonants=13

--- capitalize_words_manual (vs. built-in .title()) ---
  Manual: 'The Quick Brown Fox'
  Built-in .title(): 'The Quick Brown Fox'

--- split_and_rejoin ---
  Input: 'apple,  banana ,cherry,  date'
  Output: 'apple | banana | cherry | date'

--- mask_string ---
  mask_string('1234567890123456') = '************3456'
  mask_string('12') = '12'

============================================================
 Assignment: word_frequency
============================================================
  python     4
  is         3
  great      1
  easy       1
  to         1
  learn      1
  and        1
  powerful   1
  i          1
  love       1
