use Algorithm::Loops qw( NestedLoops );

my @spec = (
    [ 'static1'           ],
    [ 'ar1', 'ar2'        ],
    [ 'static2'           ],
    [ 'ar3', 'ar4', 'ar5' ],
);

NestedLoops(\@spec, sub {
    print(join(', ', @_), "\n");
});
[download]

Or closer to what you have:

use Algorithm::Loops qw( NestedLoops );

my @spec = map { ref($_) ? $_ : [$_] }  (
    'static1',
    [ 'ar1', 'ar2' ],
    'static2',
    [ 'ar3', 'ar4', 'ar5' ],
);

NestedLoops(\@spec, sub {
    print(join(', ', @_), "\n");
});
[download]

Update: Fixed bug.
Update: Added alt.