use 5.010;
use strict;
use warnings;

use Win32::API;

# Wrapper for external function with awkward interface
sub DOTP {
  # Get arguments
  my ($T, $P) = @_;

  # Prepare foreign function interface, if necessary
  state $ffi = Win32::API->new(
    'CARBONDIOXIDE',
    'double DOTP(LPDOUBLE lpT, LPDOUBLE lpP)'
  );

  # Pack arguments into memory to be passed to the function
  my $bufT = pack('d', $T);
  my $bufP = pack('d', $P);

  # Perform external call and return value
  return $ffi->Call($bufT, $bufP);
}

# Test the thing
say DOTP(300, 6);