You can use the Search Files tool in two different ways.
button. This is described in more detail in Entering Search Specifications directly.All kinds of search other than Grep use a LispWorks regular expression (regexp). For details of the syntax of LispWorks regular expressions see "Regular expression searching" in the LispWorks Editor User Guide .
All kinds of search other than Grep actually operate on editor buffers (see Displaying and swapping between buffers) rather than files. The Search Files tool creates buffers when needed, which involves some overhead. Therefore if you are searching a large number of files (or a number of large files) which are not already opened in the Editor, a Grep search is best because it operates directly on the files.
While the tool is searching, you can examine the results but you cannot change the search specifications. To stop a search, click the 
button in the toolbar.
LispWorks IDE User Guide (Windows version) - 25 Nov 2011