re = /.*_D[1-9]?\d$/m
str = '04R5714A_D15
04R5714A_D05
04R5714A_D5
04R5714A_D5546
04R5714A_D
'
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