Independent t-test with PROC MIXED

proc ttest data=anorexia (where=(treat in ("Cont","CBT"))); 
  class treat;
  var prewt;
run;

/* equal variance */
proc mixed data=anorexia (where=(treat in ("Cont","CBT"))); 
  class treat;
  model prewt = treat;
run;

/* unequal variance */
proc mixed data=anorexia (where=(treat in ("Cont","CBT"))); 
  class treat;
  model prewt = treat / DDFM=Satterthwaite;
  repeated / group=treat;
run;