If you want to loop through your entire file 5 times, then you can use seek to get back to the start of the file, then put everything inside another loop:

open my $fh,"+<four_comma.txt" or die "Cannot open text $!";
my $i=0;

for (1..5) {
    while(<$fh>){
        say $_;
        say ++$i;
    }
    seek $fh, 0, 0;
}
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