~$ perl -MO=Terse -e 'package foo; our $x; package bar;print $x+$a'
LISTOP (0x820dd70) leave [1] 
    OP (0x820e2d8) enter 
    COP (0x820cc00) nextstate 
    UNOP (0x820dd90) null [15] 
        PADOP (0x820cb90) gvsv  GV (0x8208700) *foo::x 
    COP (0x820ddb0) nextstate 
    LISTOP (0x823e218) print 
        OP (0x8205710) pushmark 
        BINOP (0x820df38) add [5] 
            UNOP (0x820dd30) null [15] 
                PADOP (0x820dcf0) gvsv  GV (0x8208700) *foo::x 
            UNOP (0x820cbb0) null [15] 
                PADOP (0x82046c0) gvsv  GV (0x820869c) *bar::a 
-e syntax OK