Re^2: truth in while condition

Even if it wasn't magical, it still wouldn't stop at that line. The two-character string being returned, 0␊, is true. The magic only matters when the last line of the file consists of a 0 without a terminating Line Feed. (It could also happen when $/ = \1;.)

(Oops, the main point of this has already been mentioned a couple of times below, though this post still brings in new information.)

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Re^3: truth in while condition (updated) by LanX (Saint) on Oct 02, 2018 at 12:32 UTC
(solved, see update) > (It could also happen when `$/ = \1;` ) This splits on single characters, including \n. But I couldn't find this behavior documented, neither in `perlvar#$INPUT_RECORD_SEPARATOR` nor `readline` `use strict; use warnings; use feature 'say'; $/ = \1; while ( $_= <DATA>) { say "<$_>"; } __DATA__ 1 0 345` [download] ---> `<1> < > <0> < > <3> <4> <5> < >` [download] update oops I misread `\1` as `"\1"` (ASCII 01), but it's a ref to literal 1, so this from perlvar applies: > `Setting $/ to a reference to an integer, scalar containing an integer, or scalar that's convertible to an integer will attempt to read records instead of lines, with the maximum record size being the referenced integer number of characters.` Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery FootballPerl is like chess, only without the dice}	[reply] [d/l] [select]

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Re^3: truth in while condition (updated)
by LanX (Saint) on Oct 02, 2018 at 12:32 UTC

> (It could also happen when $/ = \1; )

This splits on single characters, including \n.

But I couldn't find this behavior documented, neither in perlvar#$INPUT_RECORD_SEPARATOR nor readline

use strict;
use warnings;
use feature 'say';

$/ = \1;

while ( $_= <DATA>) {
    say "<$_>";
}

__DATA__
1
0
345
[download]

--->

<1>
<
>
<0>
<
>
<3>
<4>
<5>
<
>
[download]

update

oops I misread \1 as "\1" (ASCII 01), but it's a ref to literal 1, so this from perlvar applies:

> Setting $/ to a reference to an integer, scalar containing an integer, or scalar that's convertible to an integer will attempt to read records instead of lines, with the maximum record size being the referenced integer number of characters.

Cheers Rolf
_{(addicted to the Perl Programming Language :)

Wikisyntax for the Monastery
FootballPerl is like chess, only without the dice}

[reply]
[d/l]
[select]