my $N = shift;
    my $sqrt = sqrt( $N );
    my @factor = prime_factors( $N );
    return 1 if @factor == 1;
        # ... rest of the code
        return $f < $sqrt ? $f : undef;

##</code><code>##

    my $N = shift;
    my $sqrt = sqrt( $N );
    my @factor = prime_factors( $N );
    # ADD THIS LINE
    print "$_\n" for @factor;
    return 1 if @factor == 1;
        # ... rest of the code
        return $f < $sqrt ? $f : undef;

##</code><code>##

    my $N = shift;    
    my @factor = prime_factors( $N );
    # KEEP THIS LINE
    print "$_\n" for @factor;
    return 1 if @factor == 1;
        # ... rest of the code
        return $f;