In split, it is explained that split; defaults to split ' ', $_;.

\@numbers is not de-referencing but is creating a reference to the array @numbers. So @matrix will be an array of array references. Without it, the push would push all individual elements of @numbers onto @matrix, effectively creating a long one-dimensional list instead of a matrix.

G'day madM,

See the documentation for split for details of use without arguments.

There's no dereferencing occurring here. \@numbers is a reference to @numbers. Take a look at "perlreftut - Mark's very short tutorial about references" for an introduction to this subject.

push() pushes all its' args onto the array given as the first arg, so you need to dereference the numbers array iff the required end result is a n array of arrays i.e. without the de-ref, all you do is flatten out the list so numbers will end up containing a list of the elements of numbers.

In the cold light of day, I realise that some of the above response is, at the very least, misleading - instead of '...need to dereference...', I should have said '...create a reference to...'.

#!usr/bin/perl -w
use strict;

my @matrix;

while (<DATA>) 
{
   chomp;
   my @numbers = split; 
   #default variable to split upon is $_
   #default split is on spaces
   
   next unless @numbers; #skip blank lines (no characters)
   push (@matrix, \@numbers); #An array of array
}

foreach my $array_ref (@matrix)
{
   print "@$array_ref\n";
}

=Output
5 5.1 62.1
6 6.1 6.7
=cut


__DATA__

5 5.1 62.1


6 6.1 6.7
[download]

You seem to be confused about vocabulary. \@numbers takes a reference to @numbers, which is the opposite of “dereferencing“.

It is needed because the natural representation for a matrix is an array of arrays. Since a perl array can only hold scalar values, arrays of arrays are actually arrays of references to arrays. PerlLoL goes into a lot more detail about this concept.

Without the backslash, all numbers would be squashed together inside @matrix without structure. The result would effectively be a list, not a matrix.

The question about split is easy to answer by looking at the doc. Without any argument, split splits $_ on whitespace. It is equivalent to split /\s+/, except that leading whitespace in $_ is ignored.