my %hash1;
open my $IN, "file1.txt" or die $!;
my $header = <$IN>; ## use if the file has a header otherwise leave it
while(<$IN>){
  chomp $_;
  my @line = split(',',$_); ## split the line to get the sample name and its values
  $hash1{$line[0]} = 1; ## if your first column is a sample name or change it accordingly
}
close($IN);