use subs 'push';

my @a;
$_="x";

# push @a;  # Error: "Can't use an undefined value as an ARRAY reference ..."
print @a;

# Override!
sub push (\@_;@) {
  CORE::push( @{+shift},@_) ;
}

push @a;
print @a; # prints "x"

@b=("y","z");
push @a,@b;
print @a; # prints "2"