THREAD 1 THREAD 2 ---------------------------------- ---------------------------------- { T local %ENV; i -> Process's R_M remains undef m $ENV{REQUEST_METHOD} = 'GET'; e -> Process's R_M becomes GET | | { | local %ENV; v -> Process's R_M becomes undef $ENV{REQUEST_METHOD} = 'PUT'; -> Process's R_M becomes PUT print($ENV{REQUEST_METHOD}); -> Prints process's R_M (PUT) } -> Process's R_M restored to undef print($ENV{REQUEST_METHOD}); -> Prints process's R_M (undef) } -> Process's R_M restored to undef