Add a comment to point to the value used for __MAX_PERL__

(cherry picked from commit 3ffaa936e47410a206f29ab391151a4c0a729c0d)
Signed-off-by: Nicolas R <atoomic@cpan.org>

Author: atoomic

dist/Devel-PPPort/PPPort_pm.PL

@@ -106,7 +106,7 @@ my @todo_list = reverse sort keys %todo;
 # directories are empty (which should only happen during regeneration of the
 # base and todo files).).  Actually the final element is for blead (at the
 # time things were regenerated), which is 1 beyond the max version supported.
-my $INT_MAX_PERL = (@todo_list) ? $todo_list[0] - 1 : '5030000';
+my $INT_MAX_PERL = (@todo_list) ? $todo_list[0] - 1 : '5030000'; # used for __MAX_PERL__
 my $MAX_PERL = format_version($INT_MAX_PERL);
 my $INT_MIN_PERL = (@todo_list) ? $todo_list[-1] : 5003007;
 my $MIN_PERL = format_version($INT_MIN_PERL);