[1] RFC 2396 によれば:

• uric_no_slash = unreserved | escaped | ";" | "?" | ":" | "@" | "&" | "=" | "+" | "$" | ","

[2] つまり、

• uric_no_slash = <[A-Za-z0-9_.!~*'();?:@&=+$,-]> / escaped = uric - "/"

です。