C:\>perl -le"$ENV{lowerlowerlower}=1;print for keys %ENV"
USERPROFILE
HOMEDRIVE
CLIENTNAME
COMMONPROGRAMFILES
APPDATA
PROGRAMFILES
OS
PATHEXT
PROMPT
NUMBER_OF_PROCESSORS
HOMEPATH
PATH
USERDOMAIN
PROCESSOR_ARCHITECTURE
TEMP
SYSTEMDRIVE
COMSPEC
WINDIR
PROCESSOR_LEVEL
USERNAME
LOWERLOWERLOWER
PROCESSOR_IDENTIFIER
ALLUSERSPROFILE
COMPUTERNAME

C:\>