anchor.diff:  To run only when the branch starts with `features/`:
   
   ```js
  -build.branch =~ /features\/.+/
  +build.branch =~ /^features\//
   ```
   
   To run only when the branch ends with `/release-123`, such as `feature/release-123`:
   
   ```js
  -build.branch =~ /.+\/release-123/
  +build.branch =~ /\/release-123$/
   ```
   
   To run only when building a tag:
  
positive.code: To run only when building a tag beginning with a `v` and ends with a `.0`, such as `v1.0`:
  
  ```js
  build.tag =~ /v[0-9]+\.0/
  ```
  
  To run only if the message contains `[skip tests]`, case insensitive:
  
  ```js
  build.message !~ /\[skip tests\]/i
  
negative.code: # Using Conditionals
  
  The `if` parameter provides the ability to conditionally run steps.  Using C-like expressions, boolean conditions are defined to restrict the running of steps to specific circumstances. Conditionals can be used in all YAML-based pipelines.
  
  <%= toc %>
  
  