Rename a folder using part of a certain filename inside the folder - powershell

Question

I have a number of folders with a similar set of files. Each folder contains a file, among others, with filename in a certain pattern, e.g., "Result_XYZ.txt". So this file will have a unique XYZ part in each of the folders. I want to rename each of the folders using XYZ part of that specific file. Finally there are many such folders, so I'll need to do a batch rename.
It looks like a reverse task from 1, although I can't figure out how to solve my problem.
Thank you in advance!
Clarification, thanks to Keith:
I need to add that the specific filename I need to use contains several '_' symbols and a '-' symbol, so the filenames look like:
Some Result_123_ABC_A1B2_XYZ-M1.txt
So the part that I need for folder name is '123_ABC_A1B2_XYZ-M1'.
I'm trying to parse it like below but I'm only getting the last part '-M1'. Not quite familiar how to handle '_' in this case:
(Get-ChildItem -Path $Parent -Filter "Some Result_*.txt" -File -Recurse) | ForEach-Object{
Rename-Item -Path $_.DirectoryName -NewName $_.BaseName.Split('Some Result_')[-1] -whatIf
}

Answer 1

Assuming a simple structure such as:
C:\...\PARENT
├───folder1
│ Some Result_XYZ.txt
│
├───folder2
│ Some Result_ABC.txt
│
└───folder3
Some Result_DEF.txt
The following would work:
$Parent = 'c:\...\Parent'
(Get-ChildItem -Path $Parent -Filter 'Some Result_*.txt' -File -Recurse) | ForEach-Object{
Rename-Item -Path $_.DirectoryName -NewName $_.BaseName.Split('_')[-1] -whatIf
}
Note that the above Rename-Item has the -WhatIf switch specified so it can be safely tested. Remove the -WhatIf switch once you've verified the correct folders will be renamed.
Taking advantage of aliases and positional parameters, the above can be shortened to:
$Parent = 'c:\...\Parent'
(gci $Parent 'Some Result_*.txt' -af -s) | %{
ren $_.DirectoryName $_.BaseName.Split('_')[-1] -whatIf
}
Edit: Based on clarification
The following will extract everything after the first underscore in the filename:
$Parent = 'c:\...\Parent'
(Get-ChildItem -Path $Parent -Filter 'Some Result_*.txt' -File -Recurse) | ForEach-Object{
Rename-Item -Path $_.DirectoryName -NewName ($_.BaseName -replace '^.+?_') -whatIf
}
The -replace operator uses regulare expressions for matching. The match string specifies:
^ - Match must start at the beginning of the string
.+ - Match a sequence of one or more characters with the exception of <NewLine>
? - "Lazy" quantifier (matching stops at first underscore. Without this, everything up the last underscore would be matched)
_ - Literal underscore
References:
RegEx Cheat Sheet
-Replace operator