on right click on sign:
line 1 is "[Base1]"
teleport player to {_base1}
line 1 is "[Base2]"
teleport player to {_base2}
line 1 is "[Base3]"
teleport player to {_base3}
line 1 is "[Base4]"
teleport player to {_base4}
line 1 is "[Base5]"
teleport player to...