Variable substitution in tcl - object

Question

I'm running an incarnation of tcl 8.5 that has been embedded into another system.
That system will accept and correctly execute a command such as:
uniformDist minAndMax {1 10}
where uniformDist is some object to which I do not have internal visibility.
I want to be able to say something like:
set M 1000
uniformDist minAndMax {1 M}
but this does not work.
Nor does
set M 1000
uniformDist minAndMax {1 $M}
I tried:
u minAndMax {1 [eval $M]}
and
u minAndMax {1 [eval M]}
Neither of those works.
The error message is:
expected a real value: unable to convert from: "$M"Error: expected
fewer arguments [Error while parsing pair]
or
expected a real value: unable to convert from: "[eval"Error: expected
fewer arguments [Error while parsing pair]
What is the right way that tcl does this?

Answer 1

Variable substitution is expressed using $ and the variable's name (such as $M or ${M}).
This doesn't work:
uniformDist minAndMax {1 $M}
because the braces prevent substitution: $M is just the (sub)string 'dollar, upper case m'.
This works:
uniformDist minAndMax [list 1 $M]
because the arguments to list will be evaluated before the list {1 1000} is returned and passed to uniformDist.
The form "1 $M" would work too, and the command substitution [set M] can be used instead of the variable substitution above.
Documentation:
Summary of Tcl language syntax