perl -le "for($ARGV[0]=~/\-/g){my@a;map{$a[$_]++for(eval s/\-/\.\./r)}map{s/^([^,]*),?//;$1}@ARGV;print+(join'-',(grep$a[$_]==2,0..$#a)[0,-1])}"    
 
"25-40,74-93,95-120,130-149"     "31-47,84-99,107-123,137-151"

31-40
84-93
107-120
137-149