from perldoc perlref:

           For example, if you wanted a function to make a new
           hash and return a reference to it, you have these
           options:

               sub hashem {        { @_ } }   # silently wrong
               sub hashem {       +{ @_ } }   # ok
               sub hashem { return { @_ } }   # ok

           On the other hand, if you want the other meaning, you
           can do this:

               sub showem {        { @_ } }   # ambiguous (currently o
+k, but may change)
               sub showem {       {; @_ } }   # ok
               sub showem { { return @_ } }   # ok

           The leading +{ and {; always serve to disambiguate the
           expression to mean either the HASH reference, or the
           BLOCK.
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I use HoH's a lot in my code, so I try to make absolutely sure my hashes are as disambiguated as they can be.

--
Laziness, Impatience, Hubris, and Generosity.