Shift Operators

Shift Operators

Binary "<<" returns the value of its left argument shifted left by the number of bits specified by the right argument. Arguments should be integers. (See also Integer Arithmetic.)

Binary ">>" returns the value of its left argument shifted right by the number of bits specified by the right argument. Arguments should be integers. (See also Integer Arithmetic.)

Note that both << and >> in Perl are implemented directly using << and >> in C. If use integer (see Integer Arithmetic) is in force then signed C integers are used, else unsigned C integers are used. Either way, the implementation isn't going to generate results larger than the size of the integer type Perl was built with (32 bits or 64 bits).

The result of overflowing the range of the integers is undefined because it is undefined also in C. In other words, using 32-bit integers, 1 << 32 is undefined. Shifting by a negative number of bits is also undefined.

If you get tired of being subject to your platform's native integers, the use bigint pragma neatly sidesteps the issue altogether:

print 20 << 20;  # 20971520
print 20 << 40;  # 5120 on 32-bit machines, 
                 # 21990232555520 on 64-bit machines
use bigint;
print 20 << 100; # 25353012004564588029934064107520