How to wrap long lines in a text using Regular Expressions when you also need to indent the wrapped lines?

Question

How can one change the following text

The quick brown fox jumps over the lazy dog.

to

The quick brown fox +
    jumps over the +
    lazy dog.

using regex?

UPDATE1

A solution for Ruby is still missing... A simple one I came to so far is

def textwrap text, width, indent="\n"
  return text.split("\n").collect do |line|
    line.scan( /(.{1,#{width}})(\s+|$)/ ).collect{|a|a[0]}.join  indent
  end.join("\n")
end
puts textwrap 'The quick brown fox jumps over the lazy dog.', width=19, indent=" + \n    "
# >> The quick brown fox + 
# >>     jumps over the lazy + 
# >>     dog.

Answer 1

Maybe use textwrap instead of regex:

import textwrap

text='The quick brown fox jumps over the lazy dog.'

print(' + \n'.join(
    textwrap.wrap(text, initial_indent='', subsequent_indent=' '*4, width=20)))

yields:

The quick brown fox + 
    jumps over the + 
    lazy dog.