Does it say scaler found, scalar found, or string found?

Let's pick that line apart, though, and see what's happening.

push @body,             # So far so good. We're gonna push something o
+nto the array.
  "<tr><td rowspan="    # Push a string onto the array.
  ${\scalar, @$books}   # What *IS* this, anyway?
  "$Author2</td>\n"     # Another string
;                       # Done. But with what?
[download]

Not to mention the missing > in the HTML.