Bug 6679: Fix 6 perlcritic violations in C4/Reports/Guided.pm

Bug 6679: Fix 6 perlcritic violations in C4/Reports/Guided.pm

- Subroutine prototypes used at line 376, column 1.  See page 194 of PBP.  (Severity: 5)

- Bareword file handle opened at line 757, column 2.  See pages 202,204 of PBP.  (Severity: 5)

- Two-argument "open" used at line 757, column 2.  See page 207 of PBP.  (Severity: 5)

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>