Almost forgot, it's faster to convert the string manually than use $bfind().text.

test #4: 281
Code
alias test4 {
  set -l %ticks $ticks
  set -l %x 10000
  bset -t &bvar -1 $teststring
  while (%x) {
    bset -t &string -1 multi-user
    noop $bfind(&bvar,1,$bvar(&string,1-))
    bunset &string
    dec %x
  }
  echo -a test #4: $calc($ticks - %ticks)
}

alias teststring {
  return mIRC is a full featured Internet Relay Chat client for Windows that $&
    can be used to communicate, share, play or work with others on IRC $&
    networks around the world, either in multi-user group conferences $&
    or in one-to-one private discussions.
}