# Assertions in Regex

**URL:** <https://forum.xbench.net/t/assertions-in-regex/1032>\
**Category:** Technical Support\
**Created:** [June 28, 2023, 10:28am UTC](https://forum.xbench.net/t/assertions-in-regex/1032 "2023-06-28T10:28:31Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jixich93](https://yyz1.discourse-cdn.com/flex035/user_avatar/forum.xbench.net/jixich93/32/427_2.png) [@jixich93](https://forum.xbench.net/u/jixich93)\
**Post date:** [June 28, 2023, 10:28am UTC](https://forum.xbench.net/t/assertions-in-regex/1032/1 "2023-06-28T10:28:31Z")

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Hi team,  
Can we use assertion in Regular Expressions search mode?

Like, “Xinex, a.k.a. Xin”, match “Xin” which is started with a space, but doesn’t match the space.

I have tried “(?\<=[:sep:])\<X”, but it dosn’t work.

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<div class="post-metadata">

**Author:** ![pcondal](https://yyz1.discourse-cdn.com/flex035/user_avatar/forum.xbench.net/pcondal/32/305_2.png) [@pcondal](https://forum.xbench.net/u/pcondal)\
**Post date:** [July 3, 2023, 8:09am UTC](https://forum.xbench.net/t/assertions-in-regex/1032/2 "2023-07-03T08:09:33Z")

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The documentation for Xbench regex (which is POSIX Regex plus a couple of sugar syntax features) is found here: [Regular Expressions and Microsoft Word Wildcards :: ApSIC Xbench Documentation](https://docs.xbench.net/user-guide/regular-expressions/).

It’s not clear to me which strings you are trying to match. Could you please provide a small list with 3 or 4 examples of matched strings and 3 or 4 examples of not to be matched strings?