Looking for docs/explainer on powershell syntax ":Label foreach ($item in $items) { }" - powershell

Question

So hard to Google this one...
Looking for docs/explainer on the syntax :Label foreach ($item in $items) { }
I came across an interesting example in the official docs and I'm trying to wrap my head around some of the concepts used. The example I'm referencing is at the very bottom of the about_foreach page (using Get-Help) and also online here: https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_foreach?view=powershell-7.3#:~:text=%3AtokenLoop%20foreach
The example defines an AST/parser utility for showing info about where functions are defined within a given script file (pretty cool advanced example imo). There are a few concepts in the example that I've seen before and understand the usefulness of, but haven't used personally, like do/until statements and enumerator methods like $foreach.MoveNext()
But it's the first time I've seen the :myLabel for () {} syntax which seems to only be relevant to specific expressions like loops, and I'm curious about the usage of this construct (like how/can you reference this label), does anyone here make use of this or know where to find docs/explainer on it?
Thanks in advance !
Here's the full raw example from the docs in case you like clicking links:
function Get-FunctionPosition {
[CmdletBinding()]
[OutputType('FunctionPosition')]
param(
[Parameter(Position = 0, Mandatory,
ValueFromPipeline, ValueFromPipelineByPropertyName)]
[ValidateNotNullOrEmpty()]
[Alias('PSPath')]
[System.String[]]
$Path
)
process {
try {
$filesToProcess = if ($_ -is [System.IO.FileSystemInfo]) {
$_
} else {
Get-Item -Path $Path
}
$parser = [System.Management.Automation.Language.Parser]
foreach ($item in $filesToProcess) {
if ($item.PSIsContainer -or
$item.Extension -notin #('.ps1', '.psm1')) {
continue
}
$tokens = $errors = $null
$ast = $parser::ParseFile($item.FullName, ([REF]$tokens),
([REF]$errors))
if ($errors) {
$msg = "File '{0}' has {1} parser errors." -f $item.FullName,
$errors.Count
Write-Warning $msg
}
:tokenLoop foreach ($token in $tokens) {
if ($token.Kind -ne 'Function') {
continue
}
$position = $token.Extent.StartLineNumber
do {
if (-not $foreach.MoveNext()) {
break tokenLoop
}
$token = $foreach.Current
} until ($token.Kind -in #('Generic', 'Identifier'))
$functionPosition = [pscustomobject]#{
Name = $token.Text
LineNumber = $position
Path = $item.FullName
}
Add-Member -InputObject $functionPosition `
-TypeName FunctionPosition -PassThru
}
}
}
catch {
throw
}
}
}

Answer 1

A label example from Windows Powershell in Action. Labels don't come up that often. In your example, it's breaking out of both the do loop and the token loop with the label.
# loop label, break out of both loops
$target = 'outer'
:outer while (1) {
while(1) {
break $target # break or continue label
}
}