aaa
111
bbb
111
ccc
111
ddd

#!/bin/sh
while read -r line ; do
    echo "Processing $line"
done < <(grep 111 abc.txt)

./a: line 4: syntax error near unexpected token `<'
./a: line 4: `done < <(grep 111 abc.txt)'

#!/bin/bash
while read -r line ; do
    echo "Processing $line"
done < <(grep 111 abc.txt)

Processing 111
Processing 111
Processing 111

-rwxr-xr-x  1 root root 938736 May 10  2012 bash
lrwxrwxrwx. 1 root root      4 Feb 13 10:20 sh -> bash

man bash

When invoked as sh, bash enters posix mode after the startup files are read.