in reply to new to perl, syntax question

ikegami's post is technically correct.

However in the code that you presented, @name has nothing to do with @folder - this should be a "red flag"!
Something is missing here!

This uses the number of items in @name as an index into the @folder array.
While this could happen, it would be unusual absent other context.
I would be looking for some code that builds @folder based upon the elements in @name.

Update:
Furthermore, $var = $folder[@name]; would be unusual since Perl indicies are "zero-based".
$var = $folder[@name-1]; would I think, be more expected - another "red-flag".
You may sometimes see $#name instead of @name-1, but this means the same thing - the last index.

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Re^2: new to perl, syntax question
by bimleshsharma (Beadle) on Feb 20, 2012 at 12:10 UTC
    suppose you have @a= qw(1 2 3 4);
    you are writting print "\n @a"; this will print 1 2 3 4.
    if you are trying to write like...
    $p= @a, then it will give you count of array i.e. 4
    so it does not mean that if we write @a as index inside array would give the value of 4th index of array. Basically if we write code..
    $b[@a] with return nothing because bare @a return complete set of value which is not a valid index and that is passing as index in @b so of course will return blank.
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      Perl syntax can be tricky. Does this help? Or just further confuse?

      Update: I guess it confused one Monk, because I got a down vote.
      I am genuinely trying to be helpful here.
      When you write: $y[@x], you are accessing a single element of @y with the index of the scalar value of @x.

      Note: using $a and $b or @a or @b is in general not a good idea as the $a and $b variables have special meaning to Perl and are used in sort. Better is to use: x,y,z.

      However: "@a return complete set of value" this is not correct. What @a would mean is context specific. 

      #!/usr/bin/perl -w
use strict;
use Data::Dumper;

my @x= qw(1 2 3 4);
my @y= qw(7 8 9 10 11 12 13 14);

my $num = $y[@x];  # @x evaluates here to the number "4"!!!
                   # the number of elements in @x
                   # As said before this is a VERY unusual 
                   # formulation!!!
                   # It looks weird because it is weird.
                   # As mentioned above more normal would be
                   # $y[@x-1] or $y[$#x]
                   # I'm not saying that $y[@x] cannot have a defined,
                   # value but just that it is "strange" absent other
                   # context and would be worthy of a comment in the
                   # code.

print "The number in y is: $num\n";  #the 5th thing in @y!! WHOA!

#print $x[@y]; # ERROR: Use of uninitialized value in print
               # this is because: $x[8] is undefined!

# However consider this:
# here [@x] means something completely different

push @y, [@x]; # this means: assign new memory,
               # copy @x into that new memory ,
               # push a reference to that memory 
               # onto @y
               
print Dumper \@y;

__END__

The number in y is: 11  ### the 5th thing in @y
$VAR1 = [
          '7',
          '8',
          '9',
          '10',
          '11',
          '12',
          '13',
          '14',
          [
            '1',
            '2',
            '3',
            '4'
          ]
        ];

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