Re^3: Hmmm: while(), file handle and $_ gotcha

[webfiend]

Hold up. How does one variable - two, if you did what I do and use a variable for the outer read as well - equate to clutter? I'd probably remove the unused $cnt if I was going to knock clutter out.

use Modern::Perl;

while (my $line = <DATA>) {

    if ( $. % 10 == 1 ) {
        print $line;
    }

    for (0 .. 3) {
        my $important_line = <DATA>;
        print $important_line;
    }

}

I realize this is a matter of personal aesthetics, of course. I was just a little confused how declaring and using a variable (and avoiding weird behavior from <DATA>) was better than declaring an unused variable and getting the weird behavior.

[ikegami]

Using a variable is even required if you want to add error checking.

while (my $line = <DATA>) {

    if ( $. % 10 == 1 ) {
        print $line;
    }

    for (0 .. 3) {
        defined( my $important_line = <DATA> )
            or die("Premature EOF\n");

        print $important_line;
    }
}

[Porculus]

For small values of "required".

print( scalar <DATA> // die "Premature EOF\n" );

(But don't do that, because the version with the explicit variable is obviously right, whereas the version without one forces the reader to pause and wonder whether it will work or not. So it is, I suppose, required in the sense of "required by any sane coding standards" ...)