How to use variable arguments with ruby's OptionParser

I don't know ruby very well, but I'm trying to add some functionality to this script a co-worker wrote.

Basically right now it takes a few flags and standard in as input, and it uses OptionParser to parse the flags.

I want to use OptionParser to parse a selection of command line arguments similar to those of cat. So I guess my question is how would I write the command line options parsing part of cat in ruby using OptionParser

cat [OPTION]... [FILE]...

Hope that makes sense, any help is appreciated.

OPTS = {}

op = OptionParser.new do |x|
    x.banner = 'cat <options> <file>'      
    x.separator ''

    x.on("-A", "--show-all", "Equivalent to -vET")               
        { OPTS[:showall] = true }      

    x.on("-b", "--number-nonblank", "number nonempty output lines") 
        { OPTS[:number_nonblank] = true }      

    x.on("-x", "--start-from NUM", Integer, "Start numbering from NUM")        
        { |n| OPTS[:start_num] = n }

    x.on("-h", "--help", "Show this message") 
        { puts op;  exit }

end

op.parse!(ARGV)

# Example code for dealing with filenames
ARGV.each{ |fn| output_file(OPTS, fn) }

I shall leave other command line operations, as they say, as an exercise for the reader! You get the idea.

(NB: I had to invent a fictional -x parameter to demo passing a value after a flag.)

Update: I should have explained that this will leave ARGV as an array of filenames, assuming that the user has entered any.