use strict;
use warnings;
use 5.010;


my $file = "/usr/sap/SID/SYS/profile/DEFAULT.PFL";
my $search = 'dbhost';

open my $fh, '<', $file or die "open($file,ro) failed: $!";

my %seen;

LINE:
while ( my $line = <$fh> ) {

  # skip lines without search string 
  next LINE   if index( lc($line), lc($search), 0 ) < 0;

  # extract the third field of line
  my $third = ( split( m/\s+/, $line, ) )[2];

  # keep the fields uniq
  $seen{$third}++;
}
close $fh;

# show the third fields of matching lines, but only once
say join( "\n", keys %seen );