diff -up perl-5.10.0/t/op/subst.t.pos perl-5.10.0/t/op/subst.t
--- perl-5.10.0/t/op/subst.t.pos	2007-12-18 11:47:08.000000000 +0100
+++ perl-5.10.0/t/op/subst.t	2008-07-21 11:01:01.000000000 +0200
@@ -7,7 +7,7 @@ BEGIN {
 }
 
 require './test.pl';
-plan( tests => 136 );
+plan( tests => 139 );
 
 $x = 'foo';
 $_ = "x";
@@ -583,3 +583,11 @@ is($name, "cis", q[#22351 bug with 'e' s
     is($want,$_,"RT#17542");
 }
 
+{
+    my @tests = ('ABC', "\xA3\xA4\xA5", "\x{410}\x{411}\x{412}");
+    foreach (@tests) {
+       my $id = ord $_;
+       s/./pos/ge;
+       is($_, "012", "RT#52104: $id");
+    }
+}
diff -up perl-5.10.0/pp_ctl.c.pos perl-5.10.0/pp_ctl.c
--- perl-5.10.0/pp_ctl.c.pos	2007-12-18 11:47:08.000000000 +0100
+++ perl-5.10.0/pp_ctl.c	2008-07-21 12:31:50.000000000 +0200
@@ -285,7 +285,6 @@ PP(pp_substcont)
     { /* Update the pos() information. */
 	SV * const sv = cx->sb_targ;
 	MAGIC *mg;
-	I32 i;
 	SvUPGRADE(sv, SVt_PVMG);
 	if (!(mg = mg_find(sv, PERL_MAGIC_regex_global))) {
 #ifdef PERL_OLD_COPY_ON_WRITE
@@ -295,10 +294,7 @@ PP(pp_substcont)
 	    mg = sv_magicext(sv, NULL, PERL_MAGIC_regex_global, &PL_vtbl_mglob,
 			     NULL, 0);
 	}
-	i = m - orig;
-	if (DO_UTF8(sv))
-	    sv_pos_b2u(sv, &i);
-	mg->mg_len = i;
+	mg->mg_len = m - orig;
     }
     if (old != rx)
 	(void)ReREFCNT_inc(rx);