#!/usr/bin/perl
use strict;
use warnings;

my @data = grep $_, <DATA>;

print sort RowSort @data;

sub RowSort {

    my($aa) = $a =~ /\d+,(\d+)/;         
    my($bb) = $b =~ /\d+,(\d+)/;         
        
    $aa <=> $bb;       
}



__DATA__
1,64,1.4.5,1.4.6,44642850,44642850,0,27348,10028,59188,1488095,761904.64
1,128,1.4.5,1.4.6,25337850,25337850,0,19236,10276,28196,844595,864865.28
1,256,1.4.5,1.4.6,13489200,13489200,0,17792,11372,17832,449640,920862.72
1,512,1.4.5,1.4.6,6996270,6996270,0,18084,16744,19124,233209,955224.064
1,1024,1.4.5,1.4.6,3557880,3557880,0,31528,20488,35188,118596,971538.432
2,64,1.4.5,1.4.6,44642850,44642850,0,25828,9548,40128,1488095,761904.64
2,128,1.4.5,1.4.6,25337850,25337850,0,27936,10796,28696,844595,864865.28
2,256,1.4.5,1.4.6,13489200,13489200,0,12852,10692,13332,449640,920862.72
2,512,1.4.5,1.4.6,6996270,6996270,0,17184,15904,18844,233209,955224.064
2,1024,1.4.5,1.4.6,3557880,3557880,0,34068,17948,36628,118596,971538.432

##</code><code>##

The regular expression:

(?-imsx:\d+,(\d+))

matches as follows:
  
NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  \d+                      digits (0-9) (1 or more times (matching
                           the most amount possible))
----------------------------------------------------------------------
  ,                        ','
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    \d+                      digits (0-9) (1 or more times (matching
                             the most amount possible))
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------