#!perl     #Adjust for your system
use warnings;
use strict; # You did just forget these 2 lines?

my $lcount=0;		# Of course you'll need to declare your variables with my
my $userout='';
my $listfile = "your filename";

# Always check that the open worked.
open(FILE, $listfile) or die "Couldn't open $listfile: $!\n";

while(my $user = <FILE>) {

#    $user =~ s/(\r|\n)//; # windows compatibility 
    chomp $user; # Does what you were trying to do above but works on Macs as well

    $userout .= $user . ','; # Does the same.
    $lcount++;
	if ($lcount == 20) {
		print PIPE $userout; # no need to interpolate vars to print them

		# I assume this means you want to print them to ALL to PIPE 20 at a time
		$lcount=0;	

		# In which case you need to clear $userout
		$userout = '';

		#If you only want the first 20 uncomment the next line 
		# last;
	}
#    next if !$user;	#No idea what you thought this did?
}