Bash while loops are pretty readable and the above would be a nice to iterate over lines if it wasn't for that gnarly pipe, which is a common source of errors in this construct. Remember that a pipe starts a new shell. So:

  grep stuff file.txt | while read key value ; do [ "$key" = "target" ] && found="$value" ; done

where you might expect $found to end up with the value for the line that has "target" in the first column. Then you notice that darn pipe symbol. The variable found is set in a subshell that terminates and the value is lost. This is a problem every time you need to keep some sort of state when looping. If you can tolate a bash-ism then you could do:

  while read key value ; do [ "$key" = "target" ] && found="$value" ; done < <(grep stuff file.txt)

but that doesn't read as nice and isn't compatible. It does avoid a common source of problems though, and might be worth getting into muscle memory for the times it is needed.