This is strait out of the manual…

Strip Non Numeric Characters
Non numeric characters can be removed quickly from a projection with the REGEXP_REPLACE function.
Phone numbers are commonly entered in multiple formats:
• (123)456-7890
• (123) 456-7890
• 123-456-7890
• 123 456-7890
Example:
This projection removes non numeric characters to output the results in the same format (1234567890) with
the REGEXP_REPLACE function.

<quer:projection alias="SSN_Test" xmlns:quer="http://www.taleo.com/ws/integration/query">
<quer:customFunction name="REGEXP_REPLACE">
<quer:field path="Candidate,SocialSecurityNumber"/>
<quer:string>[^[:digit:]]</quer:string>
<quer:string/>
</quer:customFunction>
</quer:projection>

Regular expressions are a powerful tool that can also be used for other data transformations.