why perl joins multy list parameters to one list

Achilles_Sea has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks:

the following code will print 123456789, leaving @array2 empty.

mysub((1..5),(6..9));

sub mysub{
    
    my (@array1,@array2) = @_;
    
    print @array1;
}
[download]

I wonder why PERL will join the 2 array parameters into array1, and how could I pass several list to a sub routine?

Comment on why perl joins multy list parameters to one list Download Code

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Re: why perl joins multy list parameters to one list by JavaFan (Canon) on Oct 18, 2011 at 11:22 UTC
You do not have 2 array parameters, you have 2 lists. And the answer is: because Perl is designed to flatten lists - and arrays in list contexts are lists with the array elements. The answer to the second question is: you cannot. You can, however, pass two references to arrays to a sub: `mysub([1..5],[6..9]); sub mysub { my @array1 = @{$_[0]}; my @array2 = @{$_[1]}; }` [download]	[reply] [d/l]
Re^2: why perl joins multy list parameters to one list by Achilles_Sea (Novice) on Oct 18, 2011 at 13:12 UTC
it seems I haven't quite understood the difference between array and list. thank u very much :)	[reply]
Re: why perl joins multy list parameters to one list by moritz (Cardinal) on Oct 18, 2011 at 11:34 UTC
Note that Perl 6 flattens less eagerly, and tries hard to preserve information: `$ cat flatten.pl sub mysub(@a1, @a2) { say "a1: ", @a1.join(', '); say "a2: ", @a2.join(', '); } mysub((1..5), (6..9)); $ ./perl6 flatten.pl a1: 1, 2, 3, 4, 5 a2: 6, 7, 8, 9` [download] Perl 6 - second systems done right	[reply] [d/l]