U=`printf '\\xC7\\x87'`
T=`printf '\\xC7\\x88'`
L=`printf '\\xC7\\x89'`

<< Before the patch >>

# use regex
echo "aa$T" | env LC_ALL=en_US.UTF-8 src/grep -qi "\(a\)\1$U" && echo matched || echo not mached
matched
echo "aa$T" | env LC_ALL=en_US.UTF-8 src/grep -qi "\(a\)\1$L" && echo matched || echo not mached
matched

# use dfa
echo "a$T" | env LC_ALL=en_US.UTF-8 src/grep -qi "\(a\)$U" && echo matched || echo not mached
not mached
echo "a$T" | env LC_ALL=en_US.UTF-8 src/grep -qi "\(a\)$L" && echo matched || echo not mached
not mached

<< After the patch >>

# use regex
$ echo "aa$T" | env LC_ALL=en_US.UTF-8 src/grep -qi "\(a\)\1$U" && echo matched || echo not mached
matched
$ echo "aa$T" | env LC_ALL=en_US.UTF-8 src/grep -qi "\(a\)\1$L" && echo matched || echo not mached
matched

# use dfa
$ echo "a$T" | env LC_ALL=en_US.UTF-8 src/grep -qi "\(a\)$U" && echo matched || echo not mached
matched
$ echo "a$T" | env LC_ALL=en_US.UTF-8 src/grep -qi "\(a\)$L" && echo matched || echo not mached
matched