#showtooltip Regrowth
/cast [@mouseover,help]Regrowth;[@mouseover,harm]Wrath;[help]Regrowth;[harm]Wrath

What it does courtesy of Macroexplain.com

Show tooltip, icon, and cooldown for Regrowth for this macro on the action bar

If the unit your mouse is currently over is a friend then:
Cast Regrowth on the unit your mouse is currently over

Else, if the unit your mouse is currently over is an enemy then:
Cast Wrath on the unit your mouse is currently over

Else, if the currently targeted unit is a friend then:
Cast Regrowth on the currently targeted unit

Else, if the currently targeted unit is an enemy then:
Cast Wrath on the currently targeted unit