This is a much harder problem than you think. Try using Regexp::Common::balanced to strip out the code blocks. Unfortunately, your pattern still won't get you function names for valid C source code like:

int
foo(int bar, char ** baz)
{ 
  ...
}
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Maybe something like:

(\w+)\s*$RE{balanced}{-parens=>'()'}[^{]*$RE{balanced}{-parens=>'{}'}
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Though that will still have problems for some older C code.

Updated: Looking though CPAN finds C::Scan, which looks like it does what you want to do.

my $c = new C::Scan 'filename' => $filename;
my $arrayref = $c->fdecls;
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Updated 2: I'm a bit confused as to why you are implementing the only answer of your previous version of the same question that was stated flat out not to work by the poster.