To display the RegExp View select Window > Show View.. > Other... from the Eclipse menu and select the RegExp View from the list.

The RegExp plugin is a small tool to debug Regular Expressions.

To check if a Regular Expression is valid, press the run

If the Regular Expression contain brackets the resulting string will be colored.
The Single Step feature allows for a step by step inspection of the regular expression.
If no sub expressions (...) are defined by the user the RegExp Plug-in tries to use logical blocks for matching, otherwise the already existing subexpressions are used.
The following buttons are provided:
Reset (clears all color markers)
Step forward
Step backward