grep -i back-reference bug

[Lars Helgeland]

It seems there is a bug in the case insensitive matching in the presence
of back references. The following was observed with grep 2.4.2 on Linux,
and grep 2.5 under Cygwin (I think 2.5.1 is the latest (?), but I can't
find any 2.5.1 sources to download):

lars:~$ echo "BLABLA"| grep -wi '\(bla\)\1'
lars:~$ echo "blabla"| grep -wi '\(BLA\)\1'
lars:~$ echo "blabla"| grep -wi '\(bla\)\1'
blabla
lars:~$ echo "blabla"| grep -wi '\(BLA\)BLA'
blabla

Regards,
Lars