re = /(?=^\d+)^([78]\d{10}|[1]\d{9}|[0](?:\d{6}[78]|\d{7}[1])(?:\d{10}|\d{9}))/m
str = '85556987456
75556987456
1555698745
000000085556987456
000000075556987456
000000001556987456'
# Print the match result
str.scan(re) do |match|
puts match.to_s
end
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