while(IN){

##</code><code>##

while( <IN> ) {

##</code><code>##

Bareword found in conditional at yourscript.pl line xx.
Name "main::IN" used only once: possible typo at yourscript.pl line xx.

##</code><code>##

Bareword "IN" not allowed while "strict subs" in use at yourscript.pl line xx.
Execution of yourscript.pl aborted due to compilation errors.

##</code><code>##

use strict;
use warnings;