powershell: how to escape all regex characters from a string
PowerShell can call the exact same method:
[Regex]::Escape($regexStr)
But you could even improve your replacement by using just a single regex replace:
$regexStr -replace '[[+*?()\\.]','\$&'
However, I probably still missed a few metacharacters from that character class, so just use the [regex]::Escape method.