use strict ;

open( TEST, 'test.txt' ) || die "Couldn't open it";

my @names = () ;

while ( <TEST> )
{
    chomp ;
    my ( $lname, $fname ) = split /,/ ;
    push @names, $fname, $lname ;
}
close( TEST ) ;

open( BTEST, '>test.txt' ) ;
while ( @names )
{
    my ( $fname, $lname ) = splice @names, 0, 2 ;
    print BTEST "$fname $lname\n" ;
}
close( BTEST ) ;