Group strings with similar pattern in Ruby

Question

I have an array of filenames. A subset of these may have similar pattern like this (alphabet strings with a number at the end):

arr = %w[
  WordWord1.html
  WordWord3.html
  WordWord10.html
  WordWord11.html
  AnotherWord1.html
  AnotherWord2.html
  FileFile.html
]

How to identify the similar ones (they have identical substring, just their numbers differ) and move them to an array ?

['WordWord1.html', 'WordWord3.html', 'WordWord10.html', 'WordWord11.html']
['AnotherWord1.html', 'AnotherWord2.html']
['FileFile.html']

Answer 1

arr.group_by { |x| x[/[a-zA-Z]+/] }.values

Answer 2

filenames = ["WordWord1.html", "WordWord3.html", "WordWord10.html", "WordWord11.html", "AnotherWord1.html", "AnotherWord2.html", "FileFile.html"]
filenames.inject({}){|h,f|k = f.split(/[^a-zA-Z]/, 2).first;h[k] ||= [];h[k] << f; h}