on textexpander(abbreviation)
        set clipboardData to (the clipboard as text)
    return findAndReplaceInText(clipboardData, ".c", "[.]c")
end textexpander

on findAndReplaceInText(theText, theSearchString, theReplacementString)
    set AppleScript's text item delimiters to theSearchString
    set theTextItems to every text item of theText
    set AppleScript's text item delimiters to theReplacementString
    set theText to theTextItems as string
    set AppleScript's text item delimiters to ""
    return theText
end findAndReplaceInText