Gem::Installer#bash_prolog_script

# File tmp/rubies/ruby-4.0.0/lib/rubygems/installer.rb, line 961
  def bash_prolog_script
    if load_relative_enabled?
      <<~EOS
        #!/bin/sh
        # -*- ruby -*-
        _=_\\
        =begin
        bindir="${0%/*}"
        ruby="$bindir/#{ruby_install_name}"
        if [ ! -f "$ruby" ]; then
          ruby="#{ruby_install_name}"
        fi
        exec "$ruby" "-x" "$0" "$@"
        =end
      EOS
    else
      ""
    end
  end