Keep in mind that $replace() doesn't replace whole words, so word like "mind" will be changed to "mahnd" because of the i => ah replacement.

Instead of using $replace I'd create a hash table with original words as items and replacements as data.
  • /hmake rep
    /hadd rep about aboot
    /hadd rep after efter
    ...
$reptext($1-) will loop through the words in text and return a modified version,
Code:
alias reptext {
  var %r, %i = 1
  tokenize 32 $1-
  while %i <= $0 {
    %r = %r $iif($hget(rep,$ [ $+ [ %i ] ]),$ifmatch,$ [ $+ [ %i ] ])
    inc %i
  }
  return %r
}