Hi, this stopped working, possibly after a related change
to org-table-eval-formula 2 days ago.

|  a |  b | percent of a in b |
|----+----+-------------------|
| 10 | 20 | #ERROR            |
| 20 | 30 | #ERROR            |
#+TBLFM: $3=($1/$2)*100;%.2f%%

A simpler format string like ;%.2f also fails.
It seems the regexp doesn't allow the leading %.

This leading % appears in the manual, so this syntax is correct.
 | =$1+$2;%.2f=       | Same, format result to two decimals              |