#!/user/bin/perl
use strict;
use warnings;
use Data::Dumper;
use IO::All -utf8;

sub writeMatrix2File{
    my ( $filename , $matrix ) = @_;
    my $iol = io($filename)->lock;
    while (defined(my $line = shift @$matrix)) {
	# io($filename)->appendln(join ' ', map "$_", @$line);
	$iol->println(join ' ', map "$_", @$line)
    }
    $iol->unlock;
}

sub readMatrixFromFile{
    my $matrix;
    my ( $filename ) = @_;
    my @lines = io($filename)->chomp->slurp;
    while (defined (my $line = shift @lines)){
	my (@row)
	    = split (/\s+/, $line);
	push (@{$matrix}, \@row);
    }
    return $matrix;
}

my $matrix = [ [1, 2, 3],
	       [4, 5, 6],
	       [7, 8, 9] ];

my $filename = 'matrix.txt';

writeMatrix2File($filename, $matrix);
print Dumper readMatrixFromFile($filename);

__END__

~/PerlMonks$ perl matrix.pl
$VAR1 = [
          [
            '1',
            '2',
            '3'
          ],
          [
            '4',
            '5',
            '6'
          ],
          [
            '7',
            '8',
            '9'
          ]