Indeed. We call it Matching Dragon.

If these are guaranteed to be small HTML pieces I’d parse them with Floki or Meeseks and then apply a simpler regex on the text to get the two pieces of data you require.

Regex for HTML or XML is a hard “NO!” even if you do a two-days educational throwaway project.

That error is complaining about this part of your code specifically:

artist <> "("

The way matching on binaries works is that:

• it can match a binary literal like “(” because it knows its size
• it can bind to a variable, where the length is specified
• it can bind the rest of the binary to a variable, when it appears at the end of the match

Because artist and playcount are not at the end of the match, it’ll fail because you’re don’t match the second or third rule.

Hence @LostKobrakai’s suggestion

Close, but wrong it generates a single function with 1001 heads.

You probably meant “rather than a straight regex.” Well, it depends . In most cases Regex is just fine. Also, if you are after parsing the (contrived example) ISO8601 representation of a date, you might extract year, month and day straight away:

<<
    year :: binary-size(4), "-",
    month :: binary-size(2), "-",
    day :: binary-size(2)>> = "2019-03-20"
year
#⇒ "2019"

There is no silver bullet.