my $names    = "John 20, Bill 34... etc";
    my @elems    = split( /\s*,\s*/, $names );
    my %num2name = map{ reverse split( /\s/, $_ ) } @elems;

    my @sorted   = map{ $num2name{$_} } sort { $a <=> $b } keys %num2name;
    print "@sorted\n";