+# Define a usage string using the program name.
+exe = File.basename($PROGRAM_NAME)
+usage = "#{exe} [prune | rm <target> | mv <src> <dst>]"
+
+# Defaults
+mode_name = 'prune'
+mode = :prune
+
+# Now, if a mode was supplied, it should be in ARGV[0].
+if ARGV.length() > 0
+ mode_names = ['prune', 'rm', 'mv']
+ if mode_names.include?(ARGV.first().downcase()) then
+ # Peel the mode name off the head of the list.
+ mode_name = ARGV.shift()
+ end
+end
+
+if mode_name == 'rm' then
+ mode = :rm
+elsif mode_name == 'mv' then
+ mode = :mv
+end
+
+# Need this before referencing ExitCodes.
+require 'mailshears'
+
+# Since we removed both the executable name and the mode name (if it
+# existed) from ARGV, what remains should be the required
+# arguments.
+if (mode == :prune and (ARGV.length() != 0)) or
+ (mode == :rm and (ARGV.length() < 1)) or
+ (mode == :mv and (ARGV.length() != 2)) then
+ puts "ERROR: missing (or extra) command-line arguments."
+ puts "Usage: #{usage}"
+ Kernel.exit(ExitCodes::BAD_COMMAND_LINE)
+end
+
+cfg = Configuration.new()