One can bless only references, but all kind of references!

While the "standard" is to bless hash-refs, there are occasions where blessing array-refs or code-refs or even scalar-refs make much sense.

BUT there is no "literal notation" for scalar-refs (like [...] or sub{...} )!

That's why a do construct is used, to avoid temporary variables¹.

IIRC does TheDamian talk about this in his (recommended!) PBP book.

HTH! :)

update

¹) like

 
$temp_scalar = 5;
my $scalar_ref = \$temp_scalar;
bless $scalar_ref, ...
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