re = /^\s*(\+[0-9][0-9]\s*|0|)(7.*)/mix
str = '+41 79 123 456 78
+417612345678
076 123 456 78
07812345678
7712345678
+41 47 123 456 78
+413212345678
021 123 456 78
02212345678
3412345678'
subst = '$2'
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