This hasn't been updated in over 10 years.

This doesn't appear to have been substantially updated in 15 years,
other than being renamed multiple times.

This fails with:

lib/tk.rb:2055:in `_invoke': string contains null byte (ArgumentError)

$SAFE support is being removed and these are no longer a good example.

This causes a warning.  Switch to including a module that overrides
method_missing and calls super.

Proc.new without block no longer works in Ruby 3.  It was probably
done as a performance improvement in earlier Ruby versions, but
it hasn't been a performance improvement since lazy block
activation was added in Ruby 2.5.

Change Proc.new(&b) to just b when b is already the block argument
to the method.  I'm not sure why the Proc.new call was used in this
case, as b should already be a Proc instance.

Delete some commented out methods near where code changes were made.

Mostly from pterjan on GitHub, only the const added by me to fix a
compiler warning.

Fixes ruby#12

This doesn't appear to run correctly, even in tk 0.2.0 before the
recent $SAFE removal:

/home/jeremy/tmp/tk/lib/multi-tk.rb:2081:in `method_missing': undefined method `_is_master_of?' for #<RemoteTkIp:0x0000003c9657c5b0> (NoMethodError)

Trying to fix that by removing the protected on the method gives:

/home/jeremy/tmp/tk/lib/multi-tk.rb:2713:in `deleted?': no permission to manipulate (SecurityError)

On exit in both cases, you get:

/home/jeremy/tmp/tk/lib/tk.rb:3013:in `_invoke': can't delete "INTERP_FINALIZE_HOOK": command doesn't exist (RuntimeError)

It's certainly possible these are underlying issues with lib/remote-tk.rb
or lib/multi-tk.rb and not a problem with the sample itself, but I don't
think it's a good idea to ship a sample that is broken.

This doesn't appear to work correctly even in 0.2.0.