YARP errors on %r#pound# in isolation

[eregon]

$ bin/parse -e '%r#pound#' 
#<YARP::ParseResult:0x00007f768d813f20
 @comments=[],
 @errors=
  [#<YARP::ParseError:0x00007f768d6da910
    @location=(9...18),
    @message="Expected a closing delimiter for a regular expression.">],
 @value=
  ProgramNode(0...9)(
    [],
    StatementsNode(0...9)(
      [InterpolatedRegularExpressionNode(0...9)((0...3), [StringNode(3...9)(nil, (3...9), nil, "pound#")], (9...9), 0)]
    )
  ),
 @warnings=[]>

CRuby:

$ ruby --dump=insns -e '%r#pound#'
== disasm: #<ISeq:<main>@-e:1 (1,0)-(1,9)> (catch: FALSE)
0000 putobject                              /pound/                   (   1)[Li]
0002 leave

As a note YARP works fine with a newline after or a flag (e.g. i)