@ids = ("a", "b", "c", "d", "e", "f", "g",);

my %counts;

foreach my $id (@ids)
{
open(FILE, "list.txt" ) || die "couldn't open 2\n";
$/ = undef;

while (<FILE>) {
	if (/$id/g) {

		$counts{$id}++;
		}
		
		else { 
		
		print "$id not found\n";
		
		}
		
}

close FILE;
}

  use Data::Dumper;
  print Dumper \%counts;