# Get the input...
print "\nEnter the power (a positive integer from 1 through 9): ";
chomp(my $power = (<STDIN>));

# Quietly end if there's no input...
$power =~ m/\S/ or exit 1;

# Validate the input...
$power =~ m/^[1-9]$/
    or die "$power is not a positive integer from 1 through 9\n";