class Sass::Script::Funcall

def _perform(environment)
  args = @args.map {|a| a.perform(environment)}
  splat = @splat.perform(environment) if @splat
  if fn = environment.function(@name)
    keywords = Sass::Util.map_hash(@keywords) {|k, v| [k, v.perform(environment)]}
    return perform_sass_fn(fn, args, keywords, splat)
  end
  ruby_name = @name.tr('-', '_')
  args = construct_ruby_args(ruby_name, args, splat, environment)
  unless Functions.callable?(ruby_name)
    opts(to_literal(args))
  else
    opts(Functions::EvaluationContext.new(environment.options).send(ruby_name, *args))
  end
rescue ArgumentError => e
  message = e.message
  # If this is a legitimate Ruby-raised argument error, re-raise it.
  # Otherwise, it's an error in the user's stylesheet, so wrap it.
  if Sass::Util.rbx?
    # Rubinius has a different error report string than vanilla Ruby. It
    # also doesn't put the actual method for which the argument error was
    # thrown in the backtrace, nor does it include `send`, so we look for
    # `_perform`.
    if e.message =~ /^method '([^']+)': given (\d+), expected (\d+)/
      error_name, given, expected = $1, $2, $3
      raise e if error_name != ruby_name || e.backtrace[0] !~ /:in `_perform'$/
      message = "wrong number of arguments (#{given} for #{expected})"
    end
  elsif Sass::Util.jruby?
    if Sass::Util.jruby1_6?
      should_maybe_raise = e.message =~ /^wrong number of arguments \((\d+) for (\d+)\)/ &&
        # The one case where JRuby does include the Ruby name of the function
        # is manually-thrown ArgumentErrors, which are indistinguishable from
        # legitimate ArgumentErrors. We treat both of these as
        # Sass::SyntaxErrors even though it can hide Ruby errors.
        e.backtrace[0] !~ /:in `(block in )?#{ruby_name}'$/
    else
      should_maybe_raise = e.message =~ /^wrong number of arguments calling `[^`]+` \((\d+) for (\d+)\)/
      given, expected = $1, $2
    end
    if should_maybe_raise
      # JRuby 1.7 includes __send__ before send and _perform.
      trace = e.backtrace.dup
      raise e if !Sass::Util.jruby1_6? && trace.shift !~ /:in `__send__'$/
      # JRuby (as of 1.7.2) doesn't put the actual method
      # for which the argument error was thrown in the backtrace, so we
      # detect whether our send threw an argument error.
      if !(trace[0] =~ /:in `send'$/ && trace[1] =~ /:in `_perform'$/)
        raise e
      elsif !Sass::Util.jruby1_6?
        # JRuby 1.7 doesn't use standard formatting for its ArgumentErrors.
        message = "wrong number of arguments (#{given} for #{expected})"
      end
    end
  elsif e.message =~ /^wrong number of arguments \(\d+ for \d+\)/ &&
      e.backtrace[0] !~ /:in `(block in )?#{ruby_name}'$/
    raise e
  end
  raise Sass::SyntaxError.new("#{message} for `#{name}'")
end