do file over deepListFiles("c:\program files\oorexx\samples")
    say file
end

-- Depth first iteration
::routine deepListFiles
use strict arg directory, accumulator=(.List~new)
files = .File~new(directory)~listFiles
if files == .nil then return accumulator
do file over files
    accumulator~append(file)
    if file~isDirectory then call deepListFiles file~absolutePath, accumulator
end
return accumulator

/* Possible output */
c:\program files\oorexx\samples\api
c:\program files\oorexx\samples\api\callrxnt
c:\program files\oorexx\samples\api\callrxnt\backward.fnc
c:\program files\oorexx\samples\api\callrxnt\callrxnt.c
c:\program files\oorexx\samples\api\callrxnt\callrxnt.exe
c:\program files\oorexx\samples\api\callrxnt\callrxnt.ico
c:\program files\oorexx\samples\api\callrxnt\callrxnt.mak
c:\program files\oorexx\samples\api\callrxwn
c:\program files\oorexx\samples\api\callrxwn\backward.fnc
(etc...)