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instance method

OptionParser#def_head_option

def_head_option(*opts, &block)

# File tmp/rubies/ruby-3.0.5/lib/optparse.rb, line 1532
def define_head(*opts, &block)
  top.prepend(*(sw = make_switch(opts, block)))
  sw[0]
end

See also #define_head #complete #define #candidate also in 4.1 · 4.0 · 3.4 · 3.3 · 3.2 · 3.1