Replace every nth Occurrence in a Perl Script - regex

Question

I have text file with 10 lines. Each line has the word no_access and only that in it. I found a website that has syntax to replace every nth occurrence of some string. When I try to put it into a script, it spits out errors.
Replace every Nth occurrence
This is the script I have so far:
use strict;
use warnings;
while (<>) {
my $count = 0;
s/no_access/(++$count % 3 == 0)?"read":$&/ge;
}
print;
However, I get the error: Use of uninitialized value $_ in print.
I tried the script without the print command, but nothing happens. How do I get this script to run and perform the replacement of every third "no_access".

Answer 1

Here's another option:
use strict;
use warnings;
my $i = 0;
my $n = 3;
while (<>) {
s/no_access/read/ if !( ++$i % $n );
print;
}
Usage: perl script.pl inFile [>outFile]
The last, optional parameter directs output to a file.
Hope this helps!

Answer 2

Your code is almost correct, just move the variable declaration outside the while loop, and the print inside:
use strict;
use warnings;
my $count = 0;
while (<>) {
s/no_access/(++$count % 3 == 0)?"read":$&/ge;
print;
}
It then reads from stdin and prints to stdout, changing every 3rd occurrence as you want it to.
If you want to read in a file, change its contents, then write it again, your code could look like this:
use strict;
use warnings;
my $file = $ARGV[0];
die "usage: $0 <filename>" unless defined $file;
open(IN, "<$file") or die "Can't read $file: $!";
my $count = 0;
my $out = "";
while (<IN>) {
s/no_access/(++$count % 3 == 0)?"read":$&/ge;
$out .= $_;
}
close(IN);
open(OUT, ">$file") or die "Can't write $file: $!";
print OUT $out;
close(OUT);