I wonder if I can ask a newbie question, maybe..I’m trying to replace

<source>SOMETHING</source>

with

<code><pre>SOMETHING</pre></code>

So I can replace the entire match

iex(14)> String.replace("<source>(aaaM)</source>", ~r/<source>(.*)<\/source>/, fn match-> "<code><pre>#{match}</pre></code>" end)

**"<code><pre><source>(aaaM)</source></pre></code>"** 

But I need access to the first matched element, so (aaaM). Partly because I also want to HTML Escape it as well. Ok, I need to use the match in anonymous function…but..sadly.

iex(15)> String.replace("<source>(aaaM)</source>", ~r/<source>(.*)<\/source>/, fn match, code-> "<code><pre>#{match}</pre></code>" end) 
warning: variable "code" is unused (if the variable is not meant to be used, prefix it with an underscore)
  iex:15

** (FunctionClauseError) no function clause matching in String.replace/4    
    
    The following arguments were given to String.replace/4:
    
        # 1
        "<source>(aaaM)</source>"
    
        # 2
        ~r/<source>(.*)<\/source>/
    
        # 3
        #Function<43.65746770/2 in :erl_eval.expr/5>
    
        # 4
        []
    
    Attempted function clauses (showing 1 out of 1):
    
        def replace(subject, pattern, replacement, options) when is_binary(subject) and is_binary(replacement) or is_function(replacement, 1) and is_list(options)
    
    (elixir 1.13.1) lib/string.ex:1477: String.replace/4

I’m not sure I follow, I’m now supplying 4 arguments. Even if I parenthesises the multiple arguments for the anonymous function. Anyone point out where I am being a dummy?

Many thanks

RobL