I do not have to do the explicit setting of $RtnVal (since it is set in the subs)...     [emphasis added]

This implies that  $RtnVal is a global. Along with hdb, I'm handicapped by not having an example of the referenced code, e.g., emailagenda(), but are you aware that a subroutine, named or otherwise, that does not have an explicit return statement implicitly returns the value of the last expression evaluated within the subroutine? A situation something like the one described in the OP can be imagined via this scenario:

>perl -wMstrict -le
"our $RtnVal;
 our $SomeOtherGlobal;
 ;;
 my $coderef = sub {
   $RtnVal = $_[0];
   if ($RtnVal eq 'Ok') { $SomeOtherGlobal = 'Foo'; }
   };
 ;;
 for my $arg (qw(Ok NotOk)) {
   $RtnVal = $coderef->($arg);
   print qq{RtnVal '$RtnVal'};
   }
 ;;
 for my $arg (qw(Ok NotOk)) {
   $coderef->($arg);
   print qq{RtnVal '$RtnVal'};
   }
"
RtnVal 'Foo'
RtnVal ''
RtnVal 'Ok'
RtnVal 'NotOk'
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