dont forget cmds like set and eval to perform functions on accessing variables for example you know that set x [set y] would be the equiv of set x $y but you can also do set z 20;set y z ; set x [set $y]. now x has the vaue of 20.
eval comes in handy when you need to do things like
set x ${$name}(z)
for example
tcl>set ary(x) 3
tcl>set y ary
tcl>echo ${$y}(x) ;# attempt to use $y as an array name
Error: can’t read “$y”: no such varibale
tcl>
tcl>echo $[set y](x) an attemt to echo the value
$ary(x)
an eval completes the reference
tcl>eval echo $[set y](x)
3
tcl>
and then you could do
tcl>echo $$y(x)
Error: can’t read “y(x)”: variable isn’t array
tcl>echo $${y}(x)
$ary(x)
which then leads to
tcl>eval echo $${y}(x)
3
