Invoke executable with parameters and catch error output - powershell

Question

I need to run an executable that requires some parameters in that form
c:\Program Files\Tools\Tool -p Parameter -d .....
The executable reports something to standard output what should be ignored. The error output lines should be stored in an array of lines for further processing in PowerShell.
I tried
$err = & "c:\Program Files\Tools\Tool -p Parameter"
Invoke-Command "c:\Program Files\Tools\Tool -p Parameter" -ErrorVariable errorOutput
The former doesn't catch stderr.
The latter failed because the string contains more than the executable name. -p is not part of the executable name. If I omit the double quotes, Invoke-Command interprets the -p as abbreviation for "PipelineVariable".
How should I run the executable while getting stderr?
Edit:
Inspired by the answer of js2010 I tried this
$err = $( $output= & "c:\Program Files\Tools\Tool -p Parameter" ) 2>&1
Unfortunately the result in $err is:
Tool.exe : ==> Error: Product Bar\1.01.01 has not been found!
At line:1 char:17
+ ... = ( $out = & "c:\Program Files\Tools\Tool -p Parameter" ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (==> Error: Prod...been found!:String) [], RemoteException
+ FullyQualifiedErrorId : NativeCommandError
Obviously that's not the stderr output of Tool.exe but also some PowerShell annotation.
Edit2:
The variable $err is still unusable if the & is omitted:
$err = $( $output= "c:\Program Files\Tools\Tool -p Parameter" ) 2>&1
Tool.exe : ==> Error: Product Bar\1.01.01 has not been found!
At line:1 char:17
+ ... = ( $out = "c:\Program Files\Tools\Tool -p Parameter" ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (==> Error: Prod...been found!:String) [], RemoteException
+ FullyQualifiedErrorId : NativeCommandError

Answer 1

You can try the below with your exe
I tested it with one of mine which takes 3 arguments and it works as expected
$proc = [System.Diagnostics.Process]::Start([System.Diagnostics.ProcessStartInfo]#{
'FileName' = "C:\Users\Vincen\Desktop\test.exe"
'Arguments' = 's d qa'
'CreateNoWindow' = $true
'UseShellExecute' = $false
'RedirectStandardOutput' = $true # to get stdout to $proc.StandardOutput
'RedirectStandardError' = $true # to get stderr to $proc.StandardError
})
$output = $proc.StandardOutput
$error1 = $proc.StandardError
#$output.ReadToEnd()
$error1.ReadToEnd()
EDIT: Added PS Version
$stdderror= "Error"
Start-Process -FilePath "C:\Users\XXXX\Desktop\Test.exe" -ArgumentList 's d qa' -RedirectStandardError $stdderror -RedirectStandardOutput $stddop -Wait
Get-Content $stdderror

Answer 2

$err has the error messages. Just ( ) wouldn't work. Both variables would get both outputs. Edited for your example.
$env:path += ';c:\Program Files\Tools'
$err = $( $output = Tool -p Parameter ) 2>&1