... BUT!

use strict;
use warnings;

use Inline C => "DATA";
xyz();
__DATA__
__C__
xyz();

__DATA__
__C__

#define __XX__ unsigned

__XX__
int xyz(){ printf("hhaahah\n"); return 1; }
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Undefined subroutine &main::xyz called at a.pl line 8.
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removing any of the underscores in __XX__ fixes the problem.

whereas this does not have a problem:

use strict;
use warnings;

use Inline(C => <<'EOC');

#define __XX__ unsigned

__XX__
int xyz(){ printf("hhaahah\n"); return 1; }
EOC
xyz();
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I am neat-picking because in some of my usage, a 3rd party insists on typedef a __global__ and that messes up the whole inlining. But #define GLOBAL __global__ is a workaround.

bw, bliako