$ cat s1.sh
export FOO=BAR

$ cat s2.sh
export FOO=BAZ

$ cat test.sh
ls s?.sh
echo -n which one :
read j
source $j

$ source test.sh
s1.sh  s2.sh
which one :s1.sh

$ echo $FOO
BAR

$ source test.sh
s1.sh  s2.sh
which one :s2.sh

# echo $FOO
BAZ