Regex backtracking in HTTP::Body Perl module causes CPU exhaustion

HTTP::Body versions before 1.24_01 for Perl allow CPU exhaustion via regex backtracking on the filename of a multipart upload. For every file part, the multipart parser finds the suffix of the uploaded filename by matching the default $basename_regexp, qr/[^.]+(\.[^\\\/]+)$/, against the whole basename. A basename made of many dots and ending in a backslash makes the regex backtrack in time quadratic in its length. A remote attacker can exhaust CPU with one request, as a basename of about 32 KB takes several seconds to match and every file part is matched separately.