Mostly Ruby question: How to change file modification time?

http://www.ruby-doc.org/stdlib/ says
"
  touch(list, options = {})

Options: noop verbose

Updates modification time (mtime) and access time (atime) of file(s) in
list. Files are created if they don't exist.

  FileUtils.touch 'timestamp'
  FileUtils.touch Dir.glob('*.c'); system 'make'

[Source]
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