whats the difference between array and list in perl ?

An "Array" is a variable with allocated space in memory (noted/accessed with @x or $x[...] or [a,b,c] resp.) a "List" is either only syntax in the source, i.e. comma seperated expressions² or the mechanism for passing multiple values (e.g. when calling and returning from a sub¹) !

So your example

@list2 = (list1, list2, list3, list4); #example of list  (WRONG!)
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Shows a list at RHS whose values are assigned to an array-variable LHS.

Unfortunately in perl5 it's not simply possible to identify a list as a "literal array", because there are plenty of subtle differences, eg with @A=(a..c) these snippets $a=@A and $a=(a,b,c) produce totally different results.

UPDATE: Technically there is nothing like a "literal array", even if you construct an anonymous array reference  [a,b,c] you have a literal list a,b,c used to initialize an array!

You may want to search in the archives of the monastery ... it's really a f.a.q. ...

1) The values are passed on a internal stack which exists only temporarily.

2) The parens are only for grouping.

UPDATES: different clarifications...

"wantarray" is a misnamed feature, but it is documented accurately ("... looking for a list value").

as I already said ...the docs are not consistent...(e.g. naming "wantarray"...

@list1 = (1,2,3,4); 
@list2 = (list1, list2, list3, list4); 
@arr1 = ("1" , "2", "3", "4"); 
@arr2 = ("arr1", "arr2", "arr3", "arr4") ;
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my @arr3 = qw(value1 value2 value3 value4);
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my @arr5 = qw (quick brown fox);
my ($speed, $colour, $animal) = @arr5;
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although the list (list1, list2, list3, list4) is questionable, since it contains bare words which might be interpreteted as subroutine calls

Whether they are subroutine calls or not doesn't matter. It's a list because of the context - the RHS of a list assignment is always a list. The fact the assignment is a list assignment is caused by the LHS being an array.

qw returns a list

No, it doesn't. In Perl, it's not the operation (operator, subroutine, function) that determines whether a list or a scalar is returned - it's the context. It's always the context. qw in scalar context cannot return a list - there are no lists in scalar context.¹

in an old release it used to return an array

In which release was that? And what does "returning an array" mean? Could I push on it? Slice from it? Did it have a name? Perhaps you're confused by the fact in earlier releases qw was calculated at run-time (by doing a split), and nowadays qw is calculated at compile time.

You can assign to a list on the left side, provided the list only consists of variables....
...then assign from the array into the three variables $speed, $colour, $animal arranged in a list.

You're contradiction yourself. First you say it assigns to a list, then you say it assigns to a three variables. It's actually the latter that happens.

¹Who will be the first one to claim this time there's such a thing as lists in scalar context?

Who will be the first one to claim this time there's such a thing as lists in scalar context?

There is. Here's one:

>perl -MO=Concise -e"$x = (4,5,6)" 2>&1 | find "list"
5        <@> list sKP ->6
             ^    ^
             |    |
          list    scalar context
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That's why it's clearer to say "an expression cannot return a list in scalar context". In the above example, the list evaluates to the scalar 6.

Since you know better, why do you use such a needlessly confusing sentence?

> there are no lists in scalar context

This is - as usual - a definition conflict!

As I already pointed out there are (at least) two widespread interpretations of what "LIST" mean:

• a literal comma separated sequence of expressions visible in source code
• the realization for passing theses values at run time through an internal stack

  Take this example code:

   perl -e 'print scalar ($a++,"b","c"), $a'

  Following your explanation one might think that $a should never be incremented, since the "list" (the stack) is never built!

  But actually one gets c1 as output, since the "list" (the sequence) is evaluated step by step

  Cheers Rolf

  UPDATE: shortened post

Lists are really a special type of array - .essentially, , a list is a temporary construct that holds a series of values. The list can be "hand" generated using parentheses and the comma operator,

There are many definitions of list, so it's hard to describe what it is. Among other things, it can refer comma separated values in the source (a list literal), the operator produced by that code (a list operator) or the values the operator places on the stack (a list value).

On the other hand, the definition of array is quite clear. First and foremost, it's a type of variable. Very few if any properties are shared between arrays and lists (whichever definition you use) since lists are never variables in Perl.

Is it like when an array is created without any double quotes or single quotes, its called list ?

An array is never called a list. An array is never a list. It may return one. A list may be assigned to one.

In all of your examples, you are assigning a list to an array. You could also say you are initialising an array.

arrays   lists
vvvvvv   vvvvvvvvvv
@list1 = (1,2,3,4);
@list2 = (list1, list2, list3, list4);
@arr1  = ("1" , "2", "3", "4");
@arr2  = ("arr1", "arr2", "arr3", "arr4");
       ^
   assignments
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Arrays are ordered lists of scalars. Please take a look at perldata which explains these terms.

Yes, you can say an array contains a list (of elements). I just wanted to warn against making the incorrect assumption that lists are only found in arrays.