re = /Germany.*\K$/m
str = 'Copy_of_E2EDKA1003_PARTN
Copy_of_E2EDKA1003_PARTNsdf
Copy_of Germany _E2EDKA1003_PARTN
Copy_of_E2EDKA1003_PARTNsdfsdf
Copy_of_E2EDKA1003_PARTNs dfsdf
Copy_of_E2EDKA1003_PARTNfsd fsd f
Copy_of_Germany E2EDKA1003_PARTN sd fsd'
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