• a syntax, mostly comma separated (, is a list operator)
• a temporary stack to pass this sequence of scalars

Array is

• a @variable holding
• a data structure in memory

So @a = (1,2,3) means step by step

• array variable @a at LHS forces a list assignment
• the comma syntax denotes a list
• the list values are pushed to a stack
• the stack is assigned to the array and stored in memory in an AV

I hope it's clearer now.

If it's a consolation, Larry occasionally confused the terminology too, e.g. in wantarray :)

> (Modification of a read-only value attempted)

That's because 1,2,3 are literals which are read only. Use variables (sic) and you can change them in the loop. ;)

yep

use strict;
use warnings;
my $x = 12;
foreach my $aa ($x,$x){ $aa = 13; }
print $x;
----------

13
[download]

How about "readonly, anonymous stack" instead of list? Iam joking, enough of the nomenclature

And also for arrays:

Win8 Strawberry 5.8.9.5 (32)  Tue 11/24/2020 17:09:57
C:\@Work\Perl\monks
>perl -Mstrict -Mwarnings -l
my $x = 1;
my $y = 2;
my @z = (3, 4, 5);

$_ += 100 for @z, $x, $y;

print "$x, $y, (@z)";

for ($x, @z, $y) { $_ += 100; }

print "$x, $y, (@z)";
^Z
101, 102, (103 104 105)
201, 202, (203 204 205)
[download]

---

Give a man a fish:  <%-{-{-{-<

I hope the distinction between list and arrays is clearer now, I know its confusing.

E.g. this is a list assignment without literal list: @a = %a ,

... the hash is unpacked into a list which is packed into an array.

or here you need a literal list to init an array(-ref) : $a_ref = [ 1,2,3 ]

Please feel free to ask. :)

Cheers Rolf
_{(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery}

That's because 1,2,3 are literals which are read only. Use variables (sic) and you can change them in the loop. ;)

It took me a few times to understand this line based on the examples given further below but now this makes sense!

Perl is aliasing in for loops.

So $x = 42 is as useful as 1 = 42

HTH! :)

Cheers Rolf
_{(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery}

... you can't modify a list item in say a foreach loop ... but in the parameter list to a sub you can: $_[0] = 12 ...

Further to LanX's reply:   And, of course, one cannot modify a literal value in an argument list even though the list is passed as an array (of aliases). In no case can one modify a literal value: 1 is, let us fervently hope, always 1.

Win8 Strawberry 5.8.9.5 (32)  Tue 11/24/2020 14:56:16
C:\@Work\Perl\monks
>perl -Mstrict -Mwarnings -l
sub f { return $_[0] = 42; }

my $x = 88;
print f($x);
print   $x;

print f(99);
^Z
42
42
Modification of a read-only value attempted at - line 1.
[download]

Thank you for providing your examples demonstrating how variables, but not literals, can be modified in a list via a for loop or subroutine.

f(99) ok that's reasonable.