Capture nth element of a file

[jet speed]

Hi All,
I need some help with the blow.

I have a an input file with the below data

1835
1836
1837
1838
1839
183A
183B
183C
183D


#!/usr/bin/perl
use strict;
use warnings;

my $filename;
$filename = "input.txt" ;
open (FILE, "< $filename" ) or die "Could not open $filename: $!";
while (<FILE>) {
 chomp;
print "$_ \n";
}

I can successfully read the file with this, what i want to achive is to
capture every 4 th element of the input file into a variable ex: $A.
that would be
1838
183C

Any help would be much appreciated.

Regds
Sj