Type conversion can help you count special characters in a text. For example, if you'd like to find out the number of tab characters in a text, you should do this:
@([Byte][char]$text -eq 9).Count
This line will convert the characters in $text into bytes and uses -eq to filter only the character code for tabs (which is the number 9). Next, @() ensures that the result is an array so that you can use Count to check the number of found characters.