in reply to accessing variable vaule outside for loop

If your intent is to reverse the @number array, why not write it like this? 

my @number = (1,2,3,4);
my @rev = reverse @number;
print "@rev\n";

[download]
See reverse. If that is not your intent, please clarify.

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Re^2: accessing variable vaule outside for loop
by gaurav (Sexton) on Jul 06, 2013 at 11:26 UTC

    I want to do it without using any predefine function

[reply]

      In Perl arrays, the index '-1' accesses the last element in the array. '-2' accesses the second-to-last. ...and so on, down to '- scalar @array', which will be the same element as '$array[0]'.

      This makes it easy to simultaneously count upward and downward; just do a numeric negation of sign, and adjust for off-by-one.

      @numbers = ( 100, 200, 300, 400, 500 );

$reversed[$_-1] = $numbers[-$_] for 1 .. @numbers;

print "$_\n" for @reversed;

      [download]

      Here's just about the only useful use of $[ (which should be avoided, even here).

      @numbers = ( 100, 200, 300, 400, 500 );

{
  no warnings 'deprecated';
  local $[ = 1;             # Don't do this... example only.

  $reversed[$_] = $numbers[-$_] for 1 .. @numbers;
}

print "$_\n" for @reversed;

      [download]

      Dave

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[d/l]
[select]

        The array index negate-adjust trick (easily encapsulated in a subroutine) is particularly useful when dealing with 'large' arrays, the reversed elements of which can then be accessed in-place: no reversed copy, possibly quite expensive in terms of space, need be made.

[reply]
      I want to do it without using any predefine function

      I.e., "This is homework".

[reply]

      try the push function to add an element to an array.

[reply]

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