Is there a way to automatically specify a custom format for links in slack?

Question

I regularly post links from Github, Jira and others into Slack. Is there a simple way to set up a regex to process links?

Example 1: The text for the link https://github.com/my_org/main_project/pull/4208 would automatically be PR-4208.

Example 2: The text for the link https://my-org.atlassian.net/browse/ENG-123 would automatically be ENG-123.