# [] constructs an anonymous array, so we use that.
    # several ways to do it - choose any (not all :-)

    my $anon_array = [];  # gimme an anonymous array and
                          # assign it to $anon_array
    @$anon_array = @line; # assign to the anonymous array 
    push(@matrix, $anon_array);

    # shortcut:
    $anon_array = [ @line ];
    push(@matrix, $anon_array);

    # compacting further: split returns a list, use that
    # to populate an anonymous array on the fly, push that
    # (the SCALAR value which is an array reference) onto
    # the array @matrix
    push(@matrix, [split(/\s+/, $filecontents[$i])]); 
}