@arr = ('c1,s1,d1','c2,s2,d2','c1,s1,d2','c1,s2,d3');
@arr = grep{ /(.+),/;
             !$seen{$1}++
           } @arr;
print join$/,@arr;

##</code><code>##

c1,s1,d1
c2,s2,d2
c1,s2,d3