use warnings;
use strict;
use IO::File;

my ( $sum_orig, $sum_new, $lines, $lines_new );
open my $out, ">", "reorganized.txt" or die $!;

while (<DATA>)
{
    my ( $size, $file ) = split;
    $sum_orig += $size;
    if ( defined ( $_ = <DATA> ) )
    {
        my ( $size2, $file2 ) = split;
        $sum_orig += $size2;

        my $max = $size > $size2 ? $size2 : $size;
        my $rejigger = int rand($max/2);

        my $tmp2 = $size - $rejigger;
        my $tmp1 = $size2 + $rejigger;
        $out->printf("%-7d %s\n", $tmp1, $file);
        $out->printf("%-7d %s\n", $tmp2, $file2);
        $sum_new += $tmp1 + $tmp2;
        $lines_new += 2;
        $lines++;
    }
    $lines++;
}

print "Original average: ", $sum_orig / $lines, $/;
print "     New average: ", $sum_new / $lines_new, $/;

__DATA__
4329   file1
12311  file2
657    file3
4271   file4
20     file5
10001  file6