BUG in tr when lowercase letters 'o', 'p' & 'e' file names in the same directory

[Gaafer Goreish]

Hi,
I discovered that if there is a file with the one lowercase letter name 'o'
or 'p'  or 'e' in the same directory where the tr command is executed it
generates an error or unexpected result.
Following is the the simple commands used to re-produce this bug

address@hidden:# echo hello | tr [:lower:] [:upper:]
HELLO
address@hidden:# touch o
address@hidden:# echo hello | tr [:lower:] [:upper:]
tr: misaligned [:upper:] and/or [:lower:] construct
address@hidden:# rm o
address@hidden:# echo hello | tr [:lower:] [:upper:]
HELLO
address@hidden:# touch p
address@hidden:# echo hello | tr [:lower:] [:upper:]
tr: misaligned [:upper:] and/or [:lower:] construct
address@hidden:# rm p
address@hidden:# echo hello | tr [:lower:] [:upper:]
HELLO
address@hidden:# touch e
address@hidden:# echo hello | tr [:lower:] [:upper:]
hello
address@hidden:# rm e
address@hidden:# echo hello | tr [:lower:] [:upper:]
HELLO
address@hidden:#


Thanks,
Gaafer Goreish