4a5,27
> # First, let's fool around a little.
> 
> var=23
> 
> echo "\$var   = $var"           # $var   = 23
> # So far, everything as expected. But ...
> 
> echo "\$\$var  = $$var"         # $$var  = 4570var
> #  Not useful ...
> #  \$\$ expanded to PID of process being executed,
> #+ and "var" is echoed as plain text.
> #  (Thank you, Jakob Bohm, for pointing this out.)
> 
> echo "\\\$\$var = \$$var"       # \$$var = $23
> #  As expected. The first $ is escaped and pasted on to
> #+ the value of var ($var = 23 ).
> #  Meaningful, but still not useful. 
> 
> # Now, let's start over and do it the right way.
> 
> # ============================================== #
> 
> 
14,15c37,44
< eval a=\$$a
< echo "Now a = $a"      # Now a = z
---
>   eval a=\$$a
> # ^^^        Forcing an eval(uation), and ...
> #        ^   Escaping the first $ ...
> # ------------------------------------------------------------------------
> # The 'eval' forces an update of $a, sets it to the updated value of \$$a.
> # So, we see why 'eval' so often shows up in indirect reference notation.
> # ------------------------------------------------------------------------
>   echo "Now a = $a"    # Now a = z
38a68
>