"Using References" in perlref says:

Using References

That's it for creating references. By now you're probably dying to know how to use references to get back to your long-lost data. There are several basic methods.

1. Anywhere you'd put an identifier (or chain of identifiers) as part of a variable or subroutine name, you can replace the identifier with a simple scalar variable containing a reference of the correct type:

[snip]

2. Anywhere you'd put an identifier (or chain of identifiers) as part of a variable or subroutine name, you can replace the identifier with a BLOCK returning a reference of the correct type. In other words, the previous examples could be written like this:

[snip]

The first documents $#$aref, the second $#{$aref}. $aref->$#* is documented by example further down in the "Postfix Dereference Syntax" section.