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

for iterates over a list, everything in brackets is expanded (the only exception are ranges ). So <> will create a temporary list.

while loops as long a boolean expression is true.

This can be used together with an iterator, like while($x=iter()) .

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

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

Je suis Charlie!}

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Re^2: Internally, how do for() and while() differ? by Anonymous Monk on Oct 27, 2015 at 01:23 UTC
`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 $_	[reply] [d/l] [select]
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: Internally, how do for() and while() differ?

UPDATE