added support for regexp in -c parameter, added deduplication as well

tablizer.pod

@@ -67,7 +67,7 @@ have a numer associated with it, e.g.:
    NAME(1) READY(2) STATUS(3) RESTARTS(4) AGE(5)
 
 These numbers denote the column and  you can use them to specify which
-columns you want to have in your output:
+columns you want to have in your output (see L<COLUMNS>:
 
    kubectl get pods | tablizer -c1,3
 
@@ -114,6 +114,35 @@ Example for a case insensitive search:
     kubectl get pods -A | tablizer "(?i)account"
 
 
+=head2 COLUMNS
+
+The  parameter  B<-c>  can  be  used  to  specify,  which  columns  to
+display.  By default  tablizer numerizes  the header  names and  these
+numbers can  be used to specify  which header to display,  see example
+above.
+
+However, beside  numbers, you  can also  use regular  expressions with
+B<-c>, also  separated by comma. And  you can mix column  numbers with
+regexps.
+
+Lets take this table:
+
+        PID TTY          TIME CMD
+      14001 pts/0    00:00:00 bash
+      42871 pts/0    00:00:00 ps
+      42872 pts/0    00:00:00 sed
+
+We want to see only the CMD column and use a regex for this:
+
+    ps | tablizer -s '\s+' -c C
+    CMD(4)
+    bash
+    ps
+    tablizer
+    sed
+
+where "C" is our regexp which matches CMD.
+
 =head2 OUTPUT MODES
 
 There might be cases  when the tabular output of a  program is way too