How can I tell if a number is a power of 2?

larryk has asked for the wisdom of the Perl Monks concerning the following question:

I understand the binary representation of such a number will be a 1 with zero or more trailing 0s so with that in mind I rather sheepishly offer the following:

sub is_power_of_2 {
    my $number = shift;
    sprintf('%b',$number) =~ /^10*$/ ? 1 : 0;
}
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What is the most efficient way to shift that 1 to the other end so I can compare the value to 1 instead of using this horrible regex. Or is there a quicker way?

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