Perl reading file, printing unique value from a column

Question

I am new to perl, and i\'d like to achieve the following with perl.

I have a file which contain the following data:

/dev/hda1 /boot ext3 rw          


        

Answer 1

perl -anE '$s{$F[2]}++ }{say for keys %s' file

or

perl -anE '$s{$_}++ or say for $F[2]' file