my $bps = 32;
my $fmt = 3;

my %template = (
  "32,3" => 'd',#  A double-precision float in native format.
  "32,1" => 'I',
  "32,2, => 'i',
  # ... add the other formats as you need
);

my $rawdata = get_raw_data_from_C_library();

my $t = $template{ "$bps,$fmt" }
    or die "Couldn't find an unpack template for $bps BPS, format $fmt";
my @samples = unpack $template, $rawdata;