re = /^((?:\+?3)?8)?[\s\-\(]*?(0\d{2})[\s\-\)]*?(\d{3})[\s\-]*?(\d{2})[\s\-]*?(\d{2})$/m
str = '0670000000
0960000000
0970000000
0980000000
0500000000
0660000000
0950000000
0990000000
0900000000
0560000000
0570000000
0910000000
0920000000
0940000000
+380670000000
+380960000000
+380970000000
+380980000000
+380500000000
+380660000000
+380950000000
+380990000000
+380900000000
+380560000000
+380570000000
+380910000000
+380920000000
+380940000000'
subst = '$1($2)$3-$4-$5'
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