n which version of Perl did that become true?

Since 5.8.4.

$ perl583 -le '@a=(1,2); $r1 = \$a[0]; @a=sort@a; $r2 = \$a[0];print "
+yes"if $r1 == $r2'
$ perl584 -le '@a=(1,2); $r1 = \$a[0]; @a=sort@a; $r2 = \$a[0];print "
+yes"if $r1 == $r2'
yes
$
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Dave.