Question

I am getting an error while trying to sort a simple array…
The ERROR reads: “use of uninitialized value in numeric comparison (<=>) at file.pl line #”

#!/usr/bin/perl
use strict
use wardings
use Data::Dumper
my @array
my $array
$array[1]= 5
$array[2]= 2
$array[3]= 3
$array[4]= 4
$array[5]= 1
sub numerically {$a <=> $b}
my @sortedarray = sort numerically @array;

print "@sortedarray\n";

I am just trying to sort the array to get:

 1 2 3 4 5

I am new at perl so this might just be something stupid, but please help me… Thanks

Answer 1

Arrays are indexed starting at 0. The error comes from trying to sort the array when $array[0] is undefined.

Update: Also, in perl, one would write:

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
my @array = qw(1 2 3 4 5);
sub numerically {$a <=> $b}
my @sortedarray = sort numerically @array;

print "@sortedarray\n";

There is no point in declaring $array — that would be a scalar. You are only working with the array @array, even though it is called with a $. Please read the perl documentation.