It depends on how your perl is compiled. Perl usually uses 32-bit integers on common platforms, but 64-bit is available on most.

See 'perldoc Config' from the command line, and look for the ivsize key.

Update: Normally, bitwise operators force numeric values into the unsigned integer type, UV. They can be done on a string, as well, with vec to help. Be careful about bit and byte order, they can be tricky and unportable.