Instead of using a grep to remove the current SSH_AUTH_SOCK, use a loop.

.bashrc

@@ -67,15 +67,22 @@ _find_agent_sock() {
 }
 
 _pop_agent_sock() {
-  local IFS=$'\n' REPLY SOCKS=()
+  local I IFS=$'\n' REPLY SOCKS=()
   # Read the current list of auth sockets.
   if ((${BASH_VERSINFO[0]} >= 4)); then
-    mapfile -t SOCKS < <(egrep -v "^$SSH_AUTH_SOCK\$" ~/.ssh/agents 2>/dev/null)
+    mapfile -t SOCKS <~/.ssh/agents
   else
     while read -r; do
       SOCKS+=("$REPLY")
-    done < <(egrep -v "^$SSH_AUTH_SOCK\$" ~/.ssh/agents 2>/dev/null)
+    done <~/.ssh/agents
   fi
+  # Remove the last instance of the socket in $SSH_AUTH_SOCK.
+  for ((I = (${#SOCKS[@]} - 1); I >= 0; I--)); do
+    [[ "${SOCKS[$I]}" == "$SSH_AUTH_SOCK" ]] && {
+      unset SOCKS[$I]
+      break
+    }
+  done
   # Clean up any dead sockets - this modifies the SOCKS array.
   _clean_agent_socks
   # Write the new list back to disk.