What is the difference between [Regex]::Replace() and -replace?

Question

I understood the difference between .Replace() and -replace, but what are -replace and [Regex]::Replace()?

I tested the 2 following codes, but for me the results are the exactly the same.

I also referred to PowerShell Cookbook(O'reilly), and it says

([Regex] is) extremely advanced regular expression replacement

I want to know what [Regex] can but -replace can't.

$line = "Loosen the socket by turning it#counterclockwise."
$line = $line -Replace "([a-z])#([a-z])","`$1 `$2"
$line

# Loosen the socket by turning it counterclockwise.

$line.GetType()
# IsPublic IsSerial Name                                     BaseType
# -------- -------- ----                                     --------
# True     True     String                                   System.Object

$line2 = "Loosen the socket by turning it#counterclockwise."
$line2 = [Regex]::Replace($line3,"([a-z])#([a-z])","`$1 `$2")
$line2

# Loosen the socket by turning it counterclockwise.

$line2.GetType()
# IsPublic IsSerial Name                                     BaseType
# -------- -------- ----                                     --------
# True     True     String                                   System.Object

Answer 1

The Fish's helpful answer contains good pointers, but let me frame things a little differently, in part inspired by Ansgar Wiechers' comments:

• PowerShell's -replace operator is a friendly wrapper for the .NET [Regex]::Replace() method.

  • Given that PowerShell is built on the .NET framework, it is a common pattern for PowerShell to surface .NET functionality in a simpler, higher-level fashion.

• An important difference in default behavior is that -replace is case-INsensitive by default, in line with PowerShell's behavior in general.

  • Use variant -creplace for case-sensitive replacements.

• -replace only provides a subset of the functionality provided by the various [Regex]::Replace() overloads.

  • The functionality gap has narrowed in PowerShell Core v6.1.0+, which now also offers callback functionality via a script block passed to -replace, thanks to work by Mathias R. Jessen; e.g.,
    '1 + 1 = 2' -replace '\d+', { [int] $_.Value * 2 } yields '2 + 2 = 4' and is the equivalent of:
    [regex]::replace('1 + 1 = 2', '\d+', { param($match) [int] $match.Value * 2 })

• If -replace is good enough for a given use case, use it rather than [regex]::Replace().

  • The syntax of method calls differs from the rest of PowerShell, and there are subtleties around type conversion and long-term stability of code; it is therefore generally preferable to stick with native PowerShell features (cmdlets and operators), if feasible.

  • However, if -replace doesn't provide the functionality you need, calling [regex]::Replace() directly is a great advanced option; note that Replace() also exists as an instance method, in which case it offers additional functionality - e.g., the ability to limit the number of replacements; e.g.:

    # Replace only the first two 'o' instances.
    PS> $re = [regex] 'o'; $re.Replace('fooo', '@', 2)
    f@@o