use strict;
use warnings;

foo(1, 2);
foo(1, 3);
foo(5, 2);
foo(7, 3);

sub foo {
    my ($n, $p) = @_;
    print "$n << $p   = ", $n << $p  , "\n";
    print "$n * 2**$p = ", $n * 2**$p, "\n\n";
}

__END__

1 << 2   = 4
1 * 2**2 = 4

1 << 3   = 8
1 * 2**3 = 8

5 << 2   = 20
5 * 2**2 = 20

7 << 3   = 56
7 * 2**3 = 56