you are really creating different structures, Data::Dumper shows the difference clearly:

$VAR1 = {
          'expr' => \[
                        'booya',
                        'kada'
                      ]
        };
$VAR1 = {
          'expr' => [
                      [
                        'booya',
                        'kada'
                      ]
                    ]
        };
[download]

I thing you are confused about the way array references are created in perl. Probably, you would like to use...

my %args;
$args{'expr'} = ['booya' 'kada']; # no \ required here
[download]

or

my %args;
my @ary;
@ary = ('booya', 'kada'); # use () instead of []
$args{'expr'} = \@ary;
[download]

to create

$VAR1 = {
          'expr' => [
                      'booya',
                      'kada'
                    ]
        };
[download]