If you want to learn some Perl (rather than just getting the job done — in which case you could use the split utility), the open function is the key to solve your task.

That is, read the original file line by line, and for every line, open a new file for writing, and write the line to the respective file handle. The file name would comprise a counter variable, which you increment for every line.

The orginal file can be read line by line as follows when you specify its file name on the command line:

while (my $line = <>) {
    # ... do something with $line
}
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Make an attempt yourself to fill in "...", and if you get stuck, post what you've tried so far.

A little amendment to Eliya's solution (a little more talkative )

 while <INFILE> {
  $i++;
  open OUT ">$i.txt";
  #do whatever with your line
  print OUT, "...whatever...";
  close OUT; #just to be tidy :)
}
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ok so i have to do use split command:
split -l 300 newfile.txt with looping k thank you for ur valuble suggestion

Except that that will split your file into files with 300 lines each. If you want one line each, you'll need to use `split -l 1 file.orig new.`. Also, by default, split will use two-character lowercase alpha suffixes (aa .. zz) to name the new files, so it'll run out if you split into more than 676 chunks. Check the split man page for how to increase that.

Aaron B.
My Woefully Neglected Blog, where I occasionally mention Perl.