doctext of OP (thanks to Corion's way-back machine) reformatted for easier reading:

Below code loops only once and though i have 5 lines of text in my file it only loops once,
how can i get it to loop 5 times,
i donot want to store the entire file in memory in an array.

open my $fh,"+<four_comma.txt" or die "Cannot open text $!";
my $i=0;
while(<$fh>){
  say $_;
  say ++$i;
}
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