PowerShell RegEx: How to get value of a Capture Group?

Question

I am learning RegEx for Powershell.

I have dummy email address as follow:

$emails = "
[email protected]
[email protected]
[email protected]
[email protected]
"

Below is my way to extract Email ID only (example: ks.ong88) with the help of Capture Group (.+)

$emails | Select-String -Pattern '(.+)@.+' -AllMatches |
    ForEach-Object { $_.Matches.Groups }

Below is part of the result return from commands above.

Groups    : {0, 1}
Success   : True
Name      : 0
Captures  : {0}
Index     : 2
Length    : 19
Value     : [email protected]
ValueSpan : 

Success   : True
Name      : 1
Captures  : {1}
Index     : 2
Length    : 8
Value     : ks.ong88
ValueSpan : 

Groups    : {0, 1}
Success   : True
Name      : 0
Captures  : {0}
Index     : 22
Length    : 17
Value     : [email protected]
ValueSpan : 

Success   : True
Name      : 1
Captures  : {1}
Index     : 22
Length    : 8
Value     : jyan8888
ValueSpan : 

I have tried for an hour and still struggling to get the Value within Captures:[1] Appreciate your advice.