i am not able to copy non empty files only

You want to selectively copy only files which aren't empty?

my @lines = grep { -s && "$source/*.log" } readdir ($DIR);
foreach my $file (@lines){
$newfile =~ s/\.old$/.new/;
open READFILE, "$..../$file";
open WRITEFILE, ">$d../$newfile";
[download]

You're not actually reading from READFILE, nor writing to WRITEFILE. You've merely opened them for reading and writing.

What do you mean for && "$source/*.log" to achieve? Perhaps use /pattern/ instead of "pattern".

Use File::Copy to copy it somewhere after getting the list of files.

Update: ah, you've really just stuffed the condition.

-David