\newboolean{caviardee}
\setboolean{caviardee}{false}


\newcommand{\fillme}[1]{[\ding{54}]}

\makeatletter
\newlength{\@caviar@width}

\ifthenelse{\boolean{caviardee}}%
{%
\def\caviar#1{\@caviar#1 \@empty}%
}%
{%
 \def\caviar#1{#1}%
}

\def\@caviar#1 #2{%
   \settowidth{\@caviar@width}{#1}%
   \rule{\@caviar@width}{1em}\space%
   \ifx #2\@empty\else
    \expandafter\@caviar
   \fi
   #2%
}