The fill() function formats a number by filling
its string representation.
Syntax
fill(expr1, expr2, [expr3, [expr4]])
Note:
- Return string(number(expr1)) filled with string(expr3) ["
" by default] to reachnumber(expr2) width.
- Fill is done according on bool(expr4) [true by
default]: true means filling to left, false filling to right.