the following script mimics a problem I met in a larger script.

loop-break-example-functions.sh :

#!/bin/ksh
#!/bin/bash

function loop_function {
  echo_function | while read one two three
  do
  echo $one $two $three
    echo "in loop 1 onefound = $onefound"
    if [[ $two == "BB" ]]
    then
      onefound=$one
      echo "in loop in if onefound = $onefound"
      break
    fi
    echo "in loop 2 onefound = $onefound"
  done
  echo "end onefound = $onefound"
}
function echo_function {
  while read line
  do
    echo $line
  done <<EEE
  A B C
  AA BB CC
  AAA BBB CCC
EEE
}

loop_function

I works well in ksh but not in bash. When the shell is bash, the value of variable $onefound is lost in the end.
With ksh

# ./loop-break-example-functions.sh
A B C
in loop 1 onefound =
in loop 2 onefound =
AA BB CC
in loop 1 onefound =
in loop in if onefound = AA
end onefound = AA
#

switching the 2 first lines to work with bash :

# ./loop-break-example-functions.sh
A B C
in loop 1 onefound =
in loop 2 onefound =
AA BB CC
in loop 1 onefound =
in loop in if onefound = AA
end onefound =
#

Can somebody explain the difference ? How can I make it work in bash ?

I tried giving onefound an initial value in the beginning of the function.
I saw that there is no problem when the input is more straighforward (not coming from a function). The following version is OK with both shells :

#!/bin/ksh
#!/bin/bash

function loop_function {
  while read one two three
  do
  echo $one $two $three
    echo "in loop 1 onefound = $onefound"
    if [[ $two == "BB" ]]
    then
      onefound=$one
      echo "in loop in if onefound = $onefound"
      break
    fi
    echo "in loop 2 onefound = $onefound"
  done <<EEE
  A B C
  AA BB CC
  AAA BBB CCC
EEE
  echo "end onefound = $onefound"
}

loop_function