Consider the scenario:
Regular expression: ^/[a-zA-Z.]+$
Test string: /q.
Format string: /$1
Expected format result: /
Actual format result: /q.
As soon as I change the test string so that the last character is a letter but not a dot, the format result becomes / as expected.
Regular Expression Test Utility distributed with IIRF.dll always produces the right format reselt of /, even when the test string does have a dot at the end, but not the following rewrite rule:
RewriteRule ^/[a-zA-Z.]+$ /$1