re = /\b-(\s+(?:and|to|or)(?:\s+\w+)*\s+\w+(-\w[\w-]*))/m
str = 'But seeing them playing to seven- and eight-year-olds is beautiful
The country was in the uproar of pre- and then post-independence civil war but the mood here is most often joyous'
subst = '\\2\\1'
result = str.gsub(re, subst)
# Print the result of the substitution
puts result
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html