>perl -wMstrict -le
"for (@ARGV) {
   if(/^A (?: Z | (\s.*?)) Z$/x) {
     my $grabbed = $1 // '';
     print qq{matched '$_'  grabbed '$grabbed'};
     }
   }
"  AZ  AZZ  AXZ  "A SOMETHING Z"  ASOMETHINGZ
matched 'AZZ'  grabbed ''
matched 'A SOMETHING Z'  grabbed ' SOMETHING '