Ruby 3.3 is a good opportunity to add a warning message for measure command with block.
(Although, I think no one reads the warning because (maybe) no one use it.)

I searched the commit that added measure with block but it had no desciption. #183 #184

Measure command with block is

• Not documented
• Misleading. Usage is not measure{heavy_logic_to_be_measured}.
• Hard to use as a command
• Has alternative way
• Just making IRB's command system complicated

Usage of measure with block was

# Type this in IRB session.
irb> measure do |context, code, line_no, &block|
irb>   t = Time.now
irb>   result = block.call
irb>   puts "time: #{Time.now - t}"
irb>   result
irb> end
# We already have "TIME" measure, so the actual measure command will be longer and complicated than this example.

Alternative API of measure with block

# Can write this to .irbrc
irb> IRB.conf[:MEASURE_PROC][:FOOBAR] = measure_logic_proc
# Enable it
irb> measure :foobar

# Same as `measure do end`.
irb> IRB.set_measure_callback do |*, &block| measure_logic end

Alternative workaround for measure with block

irb> t=Time.now; measure_target_code; Time.now - t

irb> def m; t = Time.now; [yield, Time.now - t]; end
irb> m { measure_target_code }

Measure with block will register a session-only measure method that you don't need to write to `.irbrc`` for reusing. For this purpose, these workaround is enough and easier than using measure command with block. That's why I think no one use it.