use strict;
use warnings;

my @lines = <DATA>;

@lines = map {[/(\d+\.\d+)/g]} @lines;
@lines = sort {$a->[1] <=> $b->[1] or $a->[0] <=> $b->[0]} @lines;

print "@$_\n" for @lines;

__DATA__
48.1 0.4 99.0 0.5
1.0 0.2 99.0 0.3
1.0 0.1 99.0 0.2
1.0 0.3 99.0 0.4
1.0 0.5 99.0 0.6
13.1 0.6 99.0 0.7
5.0 0.4 48.0 0.5
1.0 0.6 13.0 0.7

##</code><code>##

1.0 0.1 99.0 0.2
1.0 0.2 99.0 0.3
1.0 0.3 99.0 0.4
5.0 0.4 48.0 0.5
48.1 0.4 99.0 0.5
1.0 0.5 99.0 0.6
1.0 0.6 13.0 0.7
13.1 0.6 99.0 0.7