>perl -wMstrict -le
"sub fmtx (@);
 ;
 print STDERR fmtx
   [ '%3.6f', 1.23, 3 ], '---', [ '%0x', 10 ], [ '%s', 'hi', 4 ],
   qq{that's all, folks \n},
   ;
 ;
 sub fmtx (@) {
   map ref() ? sprintf($_->[0],$_->[1]) x ($_->[2] // 1) : $_, @_
   }
" 2> fmtx_stderr

>cat fmtx_stderr
1.2300001.2300001.230000---ahihihihithat's all, folks