+path=/usr/ucb:/bin:~/bin:~/tmp/bin:/usr/bin
+echo $path
+
+cd /usr
+cd /tmp
+echo ~-
+echo ~+
+
+XPATH=/bin:/usr/bin:.
+
+# yes tilde expansion
+PPATH=$XPATH:~/bin
+echo "$PPATH"
+
+# no tilde expansion
+PPATH="$XPATH:~/bin"
+echo "$PPATH"
+
+# yes tilde expansion
+export PPATH=$XPATH:~/bin
+echo "$PPATH"
+
+# no tilde expansion
+export PPATH="$XPATH:~/bin"
+echo "$PPATH"