This is METAFONT, WAITS Version 0.6 (preloaded base=plain 84.12.20)  22 DEC 1984 16:05
**expr
(EXPR.MF[MF,SYS]
gimme an expr: hide(fill unitsquare)currentpicture
>> Edge structure at line 5:
row 0: 0+ 1- |

gimme an expr: hide(picture V;fill unitsquare scaled 2;V=currentpicture)V
>> Edge structure at line 5:
row 1: 0+ 2- |
row 0: 0+ 2- 0+ 1- |

gimme an expr: totalweight V/epsilon
>> 5
gimme an expr: end
! An expression can't begin with `end'.
<inserted text> 
                0
<to be read again> 
                   end
<scantokens>  end
                 
<to be read again> 
                   ;
<forever> ...string;showall.scantokens.s0;
                                           ENDFOR
l.5 showall scantokens s0; endfor
                                 
I'm afraid I need some sort of value in order to continue,
so I've tentatively inserted `0'. You may want to
delete this zero and insert something else;
see Chapter xx of The METAFONTbook for an example.

>> 0