in reply to
perl handle and common variable
Just to clarify some terminology that it appears you may have misunderstood: At the end of your second bit of posted code, $report_handler is a file handle. A "file handle" is the operating-system level resource used by programs to interact with files (and other file-like things, like pipes, stdin, stdout, etc.).
The difference you've discovered is the difference between a bareword (or typeglob) file handle (report_handler) and a lexical file handle ($report_handler). Bareword file handles mostly exist for the sake of backwards compatibility these days. Any new code should use lexical file handles instead.