Test that command substitution invokes a subshell.

test.sh

#!/bin/sh
echo "\$ echo \$(pwd)"
echo $(pwd)  #Current directory not changed.

echo "\$ \$(cd ..)"
$(cd ..)

echo "\$ echo \$(pwd)"
echo $(pwd)  #Current directory not changed.

echo "\$ \`cd ..\`"
`cd ..`

echo "\$ echo \$(pwd)"
echo $(pwd)  #Current directory not changed.

echo "\$ echo \$(cd ..; pwd)"
echo $(cd ..; pwd)

echo "\$ echo \$(pwd)"
echo $(pwd)  #Current directory not changed.

echo "* * *"

echo "\$ cd .."
cd ..

echo "\$ echo \$(pwd)"
echo $(pwd)  #Current directory changed.

Command substitution invokes a subshell.
http://tldp.org/LDP/abs/html/commandsub.html