flowchart LR
  Start[Start]
  Stop[Stop]
  Loop(( ))
  Prefix(( ))
  Start --> Prefix
  Start --> Esc([<tt>&amp;</tt>]) --> Prefix
  Prefix --> Letter{{<tt>A</tt>..<tt>Z</tt> or <tt>a</tt>..<tt>z</tt>}} --> Loop
  Prefix --> Under([<tt>_</tt>]) --> Loop
  Loop --> Letter2{{<tt>A</tt>..<tt>Z</tt> or <tt>a</tt>..<tt>z</tt>}} --> Loop
  Loop --> Under2([<tt>_</tt>]) --> Loop
  Loop --> Digit{{<tt>0</tt>..<tt>9</tt>}} --> Loop
  Loop --> Stop

  style Start fill:#44E
  style Stop fill:#E44