How to plot from stdin multiple times

[tom]

The data input from stdin fails for the second time as follows, how can I solve this problem?

plot '-' w l
0 0
5 0
 e
replot '-' w l
                ^
         unexpected or unrecognized token

The following code works, so I thought it's not grammatical error.
Is this some kind of bug ?

plot sin(x)
replot '-' w l
0 0
5 0
 e

I know plot '-' w l, '-' w l. But I don't have all data to plot in advance. So I can't use this method.
I want to plot incrementally.

Thanks.

[tom]

Replot after data input from stdin also fails.
Why is this happens.

plot '-' w l
0 0
5 0
 e
 replot sin(x)
                 ^
         unexpected or unrecognized token