if udg_my_string == "need string" then
//some actions
else
//some actions
endif

native    GetTerrainCliffLevel    takes    real x, real y    returns    integer

function  . .  takes group g returns nothing
  local unit next

  loop
    set next = FirstOfGroup(g)
    exitwhen next=null
      ...
      call doSomethingWithUnit(next)
      ...
      call GroupRemoveUnit(g,next)
  endloop
  ...
endfunction

native GroupEnumUnitsOfPlayer takes group whichGroup, player whichPlayer, boolexpr filter returns nothing
native ForGroup takes group whichGroup, code callback returns nothing