Re^2: Internally, how do for() and while() differ?

There is no general automatism to set $_ like your example implies, that's just magic behavior of the file iterator <> in scalar context.

Um, not quite, thats part of the magic of while not readline

$ perl -MO=Deparse,-p -le "while(<>){print}"
BEGIN { $/ = "\n"; $\ = "\n"; }
while (defined(($_ = <ARGV>))) {
    print($_);
}
-e syntax OK

$ perl -MO=Deparse,-p -le "while($f=<>){print}"
BEGIN { $/ = "\n"; $\ = "\n"; }
while (defined(($f = <ARGV>))) {
    print($_);
}
-e syntax OK

$ echo hi |perl -le "while($f=<>){print}"
[download]

You see <> in scalar context didn't set $_

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Re^3: Internally, how do for() and while() differ? by LanX (Saint) on Oct 27, 2015 at 09:12 UTC
I meant while's scalar context, and only this iterator. Should be documented ( `perlsyn` ? ) Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :) Je suis Charlie!} UPDATE see perlop#IO-Operators : > If and only if the input symbol is the only thing inside the conditional of a while statement (even if disguised as a for(;;) loop), the value is automatically assigned to the global variable $_ , destroying whatever was there previously.	[reply]

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Re^3: Internally, how do for() and while() differ?
by LanX (Saint) on Oct 27, 2015 at 09:12 UTC

while's

Should be documented ( perlsyn ? )

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

Je suis Charlie!}

UPDATE

see perlop#IO-Operators :

> If and only if the input symbol is the only thing inside the conditional of a while statement (even if disguised as a for(;;) loop), the value is automatically assigned to the global variable $_ , destroying whatever was there previously.

[reply]