Array size in Perl -

i trying run code , getting output as:

#!/usr/bin/perl  @array = (1,2,3); $array[50] = 4;  $size = @array; $max_index = $#array;  print "size:  $size\n"; print "max index: $max_index\n"; 

output:

size: 51 max index: 50 

what explanation this?

in perl, array data structure representing list. list has elements. keys list called indexes. first index 0 (0).

you have started array these indexes , valus:

index value 0     1 1     2 2     3 

if set 50th index value, other indexes in between filled undef, undefined value.

you have correctly identified $#array max index, or highest or last index. if force array scalar context, give number of elements, or size. you've got well. , will, Сухой27 said in comment, last index minus one.

you can illustrate behaviour if dump out array.

use strict; use warnings; use data::printer;  @array = (1,2,3); $array[10] = 4;  p @array; 

it output following. again can see index starts @ 0, , each number between 0 , highest index there. number of elements 1 less last element's index.

[     [0]  1,     [1]  2,     [2]  3,     [3]  undef,     [4]  undef,     [5]  undef,     [6]  undef,     [7]  undef,     [8]  undef,     [9]  undef,     [10] 4 ] 

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this might confusing if come php background, array can indexes or associative , still called array. in perl called hash , not ordered.

i suggest read on how perl data structures work in perldata.