$ cat t.pl
#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my %CELLS;
my $tmp;
my $curCELL;
my $curCELLR;
while (<DATA>) {
    # skip blank lines
    next if /^\s*$/;

    # Line isn't empty, so current line is a list of field names
    # and the next line is a list of the values
    my @names = split /\s+/, $_;
    my @values = split /\s+/, <DATA>;

    $curCELL  = $values[0] if $names[0] eq 'CELL';
    $curCELLR = $values[0] if $names[0] eq 'CELLR';

    # Store the name/value pairs (if we have both keys)
    next unless defined $curCELL and defined $curCELLR;

    @{$CELLS{$curCELL}{$curCELLR}}{@names} = @values;
}

print Dumper(\%CELLS);

__DATA__
NEIGHBOUR RELATION DATA

CELL
LUC325C

CELLR     DIR     CAND   CS
LUC325B   MUTUAL  BOTH   NO

KHYST   KOFFSETP  KOFFSETN   LHYST   LOFFSETP  LOFFSETN
 3       0                    3       0

TRHYST  TROFFSETP  TROFFSETN  AWOFFSET  BQOFFSET
 2       0                     5         3

HIHYST  LOHYST  OFFSETP  OFFSETN  BQOFFSETAFR
 5       3       0                 3

CELLR     DIR     CAND   CS
LUC116A   MUTUAL  BOTH   NO

KHYST   KOFFSETP  KOFFSETN   LHYST   LOFFSETP  LOFFSETN
 3       0                    3       0

TRHYST  TROFFSETP  TROFFSETN  AWOFFSET  BQOFFSET
 2       0                     5         3

HIHYST  LOHYST  OFFSETP  OFFSETN  BQOFFSETAFR
 5       3       0                 3

CELLR     DIR     CAND   CS
LUC204A   MUTUAL  BOTH   NO

KHYST   KOFFSETP  KOFFSETN   LHYST   LOFFSETP  LOFFSETN
 3       0                    3       0

TRHYST  TROFFSETP  TROFFSETN  AWOFFSET  BQOFFSET
 2       0                     5         3

HIHYST  LOHYST  OFFSETP  OFFSETN  BQOFFSETAFR
 5       3       0                 3

CELL
LUC082B