Just use glob:

my @headers = glob '*.h';

print "@headers\n";
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Or use File::Spec if you need another directory's files

use File::Spec;

my @headers = glob File::Spec->catfile($dir, '*.h');

print "@headers\n";
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- Miller

Update: Oh, unique means recursive? Well in that case I would've done the method Eliya suggested, although Anonymous's looks good too.