phranque - 7:10 pm on Apr 4, 2012 (gmt 0)
in directory context the left-hand side/matching phrase has the current directory stripped from the url path including the trialing slash of the directory:
Note: Pattern matching in per-directory context
Never forget that Pattern is applied to a complete URL in per-server configuration files. However, in per-directory configuration files, the per-directory prefix (which always is the same for a specific directory) is automatically removed for the pattern matching and automatically added after the substitution has been done.