#!/usr/bin/perl -w
use strict;

my $output;

open(TEST, 'test.txt')   || die "Couldn't open it";
while (<TEST>) {
 chomp;
 $output .= sprintf("%s %s\n", (split /,/)[1,0] ) ;
}
close(TEST);

open(TEST, '>test.txt')   || die "Couldn't open it";
print TEST $output;
close(TEST);