re = /^Redirect\h+301\h+(\S+)\h+(\S+)/m
str = 'Redirect 301 /comment/375 http://site.com/posts/c0a323fc07
Redirect 301 /comment/2772 http://site.com/posts/76d68d4d9d
'
subst = 'rewrite ^$1/?$ $2 permanent;'
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