Re^2: Changing array by changing $

Thank you! Now it makes perfect sense. I am actually in the habit of using

foreach my $variable (@array) {
    doingStuffWith($variable);
}
[download]

I guess that also prevents the elements from being changed. Thanks again for showing me the perl 'magic'.

20081016 Janitored by Corion: Closed code tag, as per Writeup Formatting Tips

Comment on Re^2: Changing array by changing $_? Download Code

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Re^3: Changing array by changing $_? by gone2015 (Deacon) on Oct 13, 2008 at 12:41 UTC
Nope. `foreach my $foo (@bar) { $foo .= 'ack' ; ... } ;` [download] will affect the contents of the array just as surely as: `foreach (@bar) { $_ .= 'ack' ; ... } ;` [download] To avoid this you need to: `foreach (@bar) { my $s = $_ . 'ack' ; ... } ;` [download] or similar. It's genuine Perl magic. Useful once you know it. A chunk out of your backside when you don't.	[reply] [d/l] [select]
Re^3: Changing array by changing $_? by ikegami (Patriarch) on Oct 13, 2008 at 14:01 UTC
That doesn't help the fact that you are modifying a global variable ($_) without localizing it first. Why use a global variable at all! `foreach (@species) { ( my $species = $_ ) =~ s/^-//; unless (exists $refspecies{$species}) { die "$species is not in the species table\n"; } }` [download]	[reply] [d/l]
Re^3: Changing array by changing $_? by GrandFather (Saint) on Oct 13, 2008 at 20:36 UTC
Are you aware that: `use strict; use warnings; my @array = 1 .. 10; doingStuffWith ($_) for @array; print "@array"; sub doingStuffWith { $_[0] +=10; }` [download] Prints: `11 12 13 14 15 16 17 18 19 20` [download] It's aliases all the way down. Perl reduces RSI - it saves typing	[reply] [d/l] [select]
Re^3: Changing array by changing $_? by busunsl (Vicar) on Oct 13, 2008 at 12:42 UTC
No, it won't. Loop variables are always aliases for the elements of the array. So it doesn't matter whether you give them a name or not.	[reply]