diff --git a/100_core/src/gplx/Bry_find_.java b/100_core/src/gplx/Bry_find_.java
index e5a1336a2..5695ea643 100644
--- a/100_core/src/gplx/Bry_find_.java
+++ b/100_core/src/gplx/Bry_find_.java
@@ -226,6 +226,14 @@ public class Bry_find_ {
 			--cur;
 		}
 	}
+	public static int Find_bwd_while_v2(byte[] src, int cur, int end, byte while_byte) {
+		--cur;
+		while (true) {
+			if (	cur < end
+				||	src[cur] != while_byte) return cur + 1;
+			--cur;
+		}
+	}
 	public static int Find_fwd_while(byte[] src, int cur, int end, byte while_byte) {
 		while (true) {
 			if (	cur == end
diff --git a/gplx.xowa.mediawiki/src/gplx/xowa/mediawiki/includes/title/XomwMediaWikiTitleCodec.java b/gplx.xowa.mediawiki/src/gplx/xowa/mediawiki/includes/title/XomwMediaWikiTitleCodec.java
index 918d51ebe..aed7c1418 100644
--- a/gplx.xowa.mediawiki/src/gplx/xowa/mediawiki/includes/title/XomwMediaWikiTitleCodec.java
+++ b/gplx.xowa.mediawiki/src/gplx/xowa/mediawiki/includes/title/XomwMediaWikiTitleCodec.java
@@ -458,3 +458,32 @@ public class XomwMediaWikiTitleCodec implements XomwTitleFormatter {
 //			return $rxTc;
 //		}
 }
+class XomwRegexTitlePrefix {
+	// $prefixRegexp = "/^(.+?)_*:_*(.*)$/S";
+	//	 "(.+?)": greedy: same as .*
+	//	 "_*"   : spaces; allows "Talk___:_A" to be (Talk) (A)
+	//	 "(.*)" : gobble up rest;
+	//	 "/S"   : analyze
+	public static boolean preg_match(byte[][] rv, byte[] src) {
+		int len = src.length;
+
+		// look for colon
+		int colon_pos = Bry_find_.Find_fwd(src, Byte_ascii.Colon, 0, len);
+
+		// if no_colon, no match; just return bry;
+		if (colon_pos == Bry_find_.Not_found) {
+			rv[0] = src;
+			rv[1] = null;
+			return false;
+		}
+
+		// colon exists; strip any flanking underlines
+		int ns_end = Bry_find_.Find_bwd_while_v2(src, colon_pos, 0, Byte_ascii.Underline);
+		int ttl_bgn = Bry_find_.Find_fwd_while(src, colon_pos + 1, len, Byte_ascii.Underline);
+
+		// split ns / title and return true
+		rv[0] = Bry_.Mid(src, 0, ns_end);
+		rv[1] = Bry_.Mid(src, ttl_bgn, len);
+		return true;
+	}
+}
diff --git a/gplx.xowa.mediawiki/src/gplx/xowa/mediawiki/includes/title/XomwMediaWikiTitleCodecTest.java b/gplx.xowa.mediawiki/src/gplx/xowa/mediawiki/includes/title/XomwMediaWikiTitleCodecTest.java
new file mode 100644
index 000000000..1bb2a85d2
--- /dev/null
+++ b/gplx.xowa.mediawiki/src/gplx/xowa/mediawiki/includes/title/XomwMediaWikiTitleCodecTest.java
@@ -0,0 +1,36 @@
+/*
+XOWA: the XOWA Offline Wiki Application
+Copyright (C) 2012-2017 gnosygnu@gmail.com
+
+XOWA is licensed under the terms of the General Public License (GPL) Version 3,
+or alternatively under the terms of the Apache License Version 2.0.
+
+You may use XOWA according to either of these licenses as is most appropriate
+for your project on a case-by-case basis.
+
+The terms of each license can be found in the source code repository:
+
+GPLv3 License: https://github.com/gnosygnu/xowa/blob/master/LICENSE-GPLv3.txt
+Apache License: https://github.com/gnosygnu/xowa/blob/master/LICENSE-APACHE2.txt
+*/
+package gplx.xowa.mediawiki.includes.title; import gplx.*; import gplx.xowa.*; import gplx.xowa.mediawiki.*; import gplx.xowa.mediawiki.includes.*;
+import org.junit.*; import gplx.core.tests.*; import gplx.core.btries.*; import gplx.xowa.mediawiki.includes.parsers.*;
+public class XomwMediaWikiTitleCodecTest {
+	private final    XomwMediaWikiTitleCodecFxt fxt = new XomwMediaWikiTitleCodecFxt();
+	@Test  public void regexTitlePrefix() {
+		// no match
+		fxt.Test_regexTitlePrefix("a"         , "a", null);
+		// ns
+		fxt.Test_regexTitlePrefix("a:b"       , "a", "b");
+		// underscores
+		fxt.Test_regexTitlePrefix("a__:___b"  , "a", "b");
+	}
+}
+class XomwMediaWikiTitleCodecFxt {
+	private byte[][] regexTitlePrefixResult = new byte[2][];
+	public void Test_regexTitlePrefix(String src, String expd_ns, String expd_ttl) {
+		XomwRegexTitlePrefix.preg_match(regexTitlePrefixResult, Bry_.new_u8(src));
+		Gftest.Eq__str(expd_ns,  String_.new_u8(regexTitlePrefixResult[0]));
+		Gftest.Eq__str(expd_ttl, String_.new_u8(regexTitlePrefixResult[1]));
+	}
+}