use Data::Dumper;

@a=('bar');
print Dumper(\@a);

push @{$a[0]}, "foo";

print Dumper(\@a);
print Dumper(\@bar);

##</code><code>##

$VAR1 = [
          'bar'
        ];
$VAR1 = [
          'bar'
        ];
$VAR1 = [
          'foo'
        ];