re = /[0-9]{3}(\-|\ |\ )?[0-9]{3}(\-|\--|\ )?-?[0-9]{4}/m
str = '998-999-9999
788 566-9876
763 535 6788
452456-7666
6765267892'
subst = ''
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