overlay

>>-overlay(new-+---------------------------------------+-)-----><
               +-,--+---+--+-------------------------+-+
                    +-n-+  +-,--+--------+--+------+-+
                                +-length-+  +-,pad-+

Returns a copy of the receiving string, which, starting at the [n] th character, is overlaid with the string [new] , padded or truncated to length [length] . The overlay can extend beyond the end of the receiving string. If you specify [length] , it must be a positive whole number or zero. The default value for [length] is the length of [new] . If [n] is greater than the length of the receiving string, padding is added before the [new] string. The default [pad] character is a blank, and the default value for [n] is 1. If you specify [n] , it must be a positive whole number.

String class - overlay method

"abcdef"~overlay(" ",3)         ->    "ab def"
"abcdef"~overlay(".",3,2)       ->    "ab. ef"
"abcd"~overlay("qq")            ->    "qqcd"
"abcd"~overlay("qq",4)          ->    "abcqq"
"abc"~overlay("123",5,6,"+")    ->    "abc+123+++"