awk '
        /PREF:/ && /AVAIL:/ {
           for(i=1;i<NF;i++) {
              if($i == "PREF:") P[$(i+1)];
              if($i == "AVAIL:") A[$(i+1)];
           }
        }
        /Preferred instances/ {
                P[$NF]
        }
        /Available instances/ {
                A[$NF]
        }
        END {
                printf ( "%s:", "Preferred instances" )
                for ( k in P )
                        printf ( " %s", k )

                printf ( "\n%s:", "Available instances" )
                for ( k in A )
                        printf ( " %s", k )

                printf "\n"
        }
'