http://qs1969.pair.com?node_id=743238

sandy1028 has asked for the wisdom of the Perl Monks concerning the following question:

Difference between my($Files) = @_; and my $Files = @_

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Re: Difference between my ($foo) & my $foo
by GrandFather (Saint) on Feb 12, 2009 at 07:50 UTC 
    my($Files) = @_;

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    List context.

    my $Files = @_;

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    Scalar context.

    True laziness is hard work
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Re: Difference between my ($foo) & my $foo
by ELISHEVA (Prior) on Feb 12, 2009 at 08:52 UTC
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Re: Difference between my ($foo) & my $foo
by Anonymous Monk on Feb 12, 2009 at 07:50 UTC 
    $ perl -MO=Deparse,-p -
my($Files) = @_;
my $FilesR = @_;


^D
(my($Files) = @_);
(my $FilesR = @_);
- syntax OK

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    Its list context versus scalar context, example 
    
@_ = 0 .. 3;
my( $one, $two, $three ) = @_;
print "one($one)two($two)three($three)\n";
( $one, $two, $three ) = scalar @_;
print "one($one)two($two)three($three)\n";

__END__
one(0)two(1)three(2)
one(4)two()three()

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Re: Difference between my ($foo) & my $foo
by planetscape (Chancellor) on Feb 14, 2009 at 05:03 UTC
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Re: Difference between my ($foo) & my $foo
by repellent (Priest) on Feb 12, 2009 at 19:54 UTC
    With:
    my (undef, $a, undef, $b, @rest, $c) = (1, 2, 3, 4, 5, 6, 7, 8);

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    Now:
    • @rest will be greedily assigned: @rest = (5, 6, 7, 8)
    • the other variables are respectively assigned: ($a, $b, $c) = (2, 4, undef)

    Then:
    my $count   = @rest; # 4 - because there are four items (scalar contex
+t)

my ($first) = @rest; # 5 - because first item is 5 (list context)

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    But:
    my $last = (11, 22, 33, 999); # 999 - because assigning LIST to scalar
+ only picks last item

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