> For the complete documentation index, see [llms.txt](https://docs.pentaho.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.pentaho.com/pdia-data-integration/10.2-data-integration/pdi-transformation-steps-reference-overview/regex-evaluation/options-regex-evaluation/settings-tab/regular-expression-evaluation-window.md).

# Regular expression evaluation window

You can test your regular expression against three different input strings using the following **Regular expression evaluation** window:

![Regular expression evaluation window](https://2745965000-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FvZoINBz5C5WnDZQlbOJQ%2Fuploads%2Fgit-blob-a77b682dc66b5db2a2de086d20c455762cc400e4%2FPDI_RegEx_Eval_Window.png?alt=media)

If your expression contains a group field, type a string in the Compare section and the option below the string will be split according to your group(s).

The window contains the following options:

| Field                                               | Description                                                                                                                                                                            |
| --------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Please enter a new regular expression or modify** | Specify your regular expression.                                                                                                                                                       |
| **Values to test**                                  | Specify the values (**Value1**, **Value2**, or **Value3**) to test your string. The background will turn green if that value is a match against your expression or red if it does not. |
| **Capture from value**                              | Displays the value of the captured string.                                                                                                                                             |
| **Captured fields**                                 | Displays the value of the captured groups.                                                                                                                                             |


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://docs.pentaho.com/pdia-data-integration/10.2-data-integration/pdi-transformation-steps-reference-overview/regex-evaluation/options-regex-evaluation/settings-tab/regular-expression-evaluation-window.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.