use strict;
use warnings;

{
    local $/;
    printInTwos(
       sort {$a <=> $b}
       split m{(?:,|\s+)}, <DATA>);   
}

sub printInTwos
{
    print(shift, q{,}, shift, qq{\n}) while @_;
}

__END__
10,20
30,10
20,70
70,80
40,90
90,100
50,50

##</code><code>##

10,10
20,20
30,40
50,50
70,70
80,90
90,100