The following program is suppose to read rs ID's of SNPs from the file 'testID' and then search them from file 'testSNP' and sends the output to testSNP.out. I through multiple print statements have debugged the program and found no error but it is not generating the output. what is the problem with this code?

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

my $rs_id;
open (my $id_file, '<testID') or die "Could not open the file: $!\n";
while ($rs_id = <$id_file>) {
findVariants($rs_id); }

close $id_file;
print "Done\n";

sub findVariants {
my ($rs_num) = @_;
open (my $in_file, '<testSNPs') or die "Could not open the file: $!\n";
my @snp = <$in_file>;
my @result= grep /$rs_num/, @snp; 
print @result;
open (my $out_file, '>>testSNPs.out');

print $out_file @result;

close $out_file;
close $in_file; 
}