like '%6' does not match '%66'?

select listid from mylist where listid like '%6';

to get all list ended with 6. but it does not match 66, 23466,
i.e., anything tht ended with 66.

if I use %66, then, it does not match %666 -- altho weird, it is
consistent.

more genereally, anything that has 6 except in the end will not
match '%6' !!!

Now i'm going to use ~ or ~*. but they are not portable. Seems that
"like" is somehow borken.

I'm using 6.5.1, and I checked the release history of 6.5.2 and 6.5.3,
in 6.5.2 there is:
Repair logic error in LIKE: should not return LIKE_ABORT
when reach end of pattern before end of text(Tom)
however, I can not upgrade now.

anybody can explain?

thanks