/usr/lib/ruby/vendor_ruby/rack/mount/strexp/tokenizer.rex is in ruby-rack-mount 0.8.3-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 | class Rack::Mount::StrexpParser
macro
RESERVED \(|\)|:|\*
ALPHA_U [a-zA-Z_]
rule
\\({RESERVED}) { [:CHAR, @ss[1]] }
\:({ALPHA_U}\w*) { [:PARAM, @ss[1]] }
\*({ALPHA_U}\w*) { [:GLOB, @ss[1]] }
\( { [:LPAREN, text] }
\) { [:RPAREN, text] }
. { [:CHAR, text] }
end
|