sub shuffle {
my $array= shift;
    my $i;
    for ($i = @$array; --$i; ) {
        my $j = int rand ($i+1);
        next if $i == $j;
        @$array[$i,$j] = @$array[$j,$i];
    }
  }  
open(NEW, "A.txt") || die "Opening A.txt: $!" ; # the original file
open(FH, ">B.txt") || die "Opening B.txt: $!" ; #  shuffle file save in this

while (<NEW>) {
    push(@lines, $_);
}
@reordered = shuffle(@lines);
foreach (@reordered) {
    print FH $_;
}
close NEW;
close FH;