Avoid subshell from pipe on dash

I have this example code:

find "$1" ! -regex "$regex" 2>/dev/null | while read line ; do
    a="$line"
done

echo ("$a") # prints nothing because of subshell

I need:

• Workaround for subshell to make $a visible outside (in global scope)
• To NOT use bash's process substitution
• To have compatible with dash, bash and korn shell

How can I achieve this? Is there any simple solution?

Use an explicit named pipe.

mkfifo named_pipe
find "$1" ! -regex "$regex" 2> /dev/null > named_pipe &

while read line; do
    a=$line
done < named_pipe