For what it is worth, that code works for me:

 $ perl ic.pl
test
Hello Ingy
[download]

Update: Following a suggestion from chatter:

#!/usr/bin/perl -w
use lib '/usr/share/perl5/Module/Install';
use Inline C => Config => BUILD_NOISY => 1, CLEAN_AFTER_BUILD => 0;
print "test\n";
greet('Ingy');

__END__
__C__
void greet(char* name) {
    printf("Hello %s\n", name);
}
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yields:

 $ perl ic.pl
test
Undefined subroutine &main::greet called at ic.pl line 5.
[download]

(Probably because the extra arguments on the 'use' line override the default behavior of look for "__C__".)