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until

An until executes its body until its condition is truthy. An until is just syntax sugar for a while with the condition negated:

until some_condition
  do_this
end

# The above is the same as:
while !some_condition
  do_this
end

break and next can also be used inside an until.

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https://crystal-lang.org/docs/syntax_and_semantics/until.html