Vista - Novice question: How I can query for a variable scope?

This is related to: RE: Issues of executing a script block in a function

1. How I can query for a variable scope?
I.e. I have a variable $a. How can I tell which scope it belongs to?
Knowing it will greatly to help with debugging! :-)

1.1. Which scope a function parameter belongs to?
1.2.1. Which scope a script (i.e. file with extension ps1) named
parameters/arguments belongs to?
1.2.2. Which scope a script block (i.e. {…}) parameter/argument belongs to?


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From "PowerShell User Guide.doc":
The PowerShell provides four labels for identifying the scope of a variable:
local
global
private
script
----------------------------------------------------

## -- cut here ------------------------------------------------

function test {
"-- function test -----------------------"
"-- local: {0}" -f $local:a
"-- global: {0}" -f $global:a
"-- private: {0}" -f $private:a
"-- script: {0}" -f $script:a
}


[string] $local:a = "I'm local"
[string] $global:a = "I'm global"
[string] $private:a = "I'm local"
[string] $script:a = "I'm script"

"-- local: {0}" -f $local:a
"-- global: {0}" -f $global:a
"-- private: {0}" -f $private:a
"-- script: {0}" -f $script:a

test

## -- cut here ------------------------------------------------

****** output *************************************************

-- local: I'm script
-- global: I'm global
-- private: I'm script
-- script: I'm script
-- function test -----------------------
-- local:
-- global: I'm global
-- private:
-- script: I'm script