re = /<!--product_template(?:(?!<!--product_template).)*?<table.*?<!--end_product_template-->/
str = '<!--product_template this is some extra text -->
<table class=\'template\'></table>
<!--end_product_template-->
non-commented text might exist in the document
<div>As will other tags</div>
<!--product_template this is some different extra text--><table class=\'template\'></table><!--end_product_template-->
<!--product_template--><p><!--end_product_template-->
<!--product_template--><!--end_product_template-->
<!--product_template--><table class=\'template\'></table><!--end_product_template-->
'
# Print the match result
str.scan(re) do |match|
puts match.to_s
end
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