--- a/src/learn.html.luan	Mon Apr 14 16:26:37 2025 -0600
+++ b/src/learn.html.luan	Tue Apr 15 13:50:58 2025 -0600
@@ -67,6 +67,8 @@
 
 <p>I suggest that you just read through these tutorials so that you get a sense for how regex and grep work.  You don't need to practice anything here.  You can come back to these tutorials later when you have a real need for regex or grep.</p>
 
+<p>The details of regex vary by implementation.  Luan use <a href="https://docs.oracle.com/javase/8/docs/api/java/util/regex/package-summary.html">Java regex</a>.
+
 <p>If you become a serious programmer, then you should have a deeper understanding of regex.  In that case I recommend the book <a href="https://www.amazon.com/Mastering-Regular-Expressions-Jeffrey-Friedl/dp/0596528124/">Mastering Regular Expressions</a>.</p>
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