re = /(\[[^\][]*]\()https?:\/\/docs\.google\.com\/document\/d\/([^\s\\\/)]+)[^\s)]*\)/m
str = '# Title
Text text text.
Text 1 text 1 text 1, abc.
More text
Bullet points
- [abc]
- [bla]
- [cba]
[Text](https://docs.google.com/document/d/unique-doc-id-here/edit)
## Title 2
More text:
- A
- B
- C
- D
Text text text text [url1](https://docs.google.com/document/d/2x2my-DRqfSidOsdve4m9bF_eEOJ7RqIWP7tk7PM4qEr) text.
**BOLD.**
## Title
Text2 text1 text3 text
[url2](https://docs.google.com/document/d/4x2mrhsqfGSidOsdve4m9bb_wEOJ7RqsWP7tk7PMPqEb/edit#bookmark=id.mbnek2bdkj8c) text.
More text here
[bla](https://docs.google.com/document/d/6an7_b4Mb0OdxNZdfD3KedfvFtdf2OeGzG40ztfDhi5o9uU/edit)
'
subst = '$1[REPLACEMENT]$3'
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