use Data::Dumper;

my %on_prop;
my %on_user;
while (<DATA>) {
	my @fields = split "\t";
	my %column_data = map {$_, shift(@fields)} qw(PROP COLOUR TXTCOL URL360 USER YOUR_NAME ETC);
	$on_prop{$column_data{PROP}} = \%column_data;
	push @{$on_user{$column_data{USER}}}, \%column_data;
}

print Dumper(\%on_prop);
print Dumper(\%on_user);
print  scalar @{$on_user{'rob'}}; # prints 2 (more than one item for this user)

__DATA__
123	Red	blue	whatever	rob	blah	blah	blah
124	Red	blue	whatever	rob	blah	blah	blah
125	Red	blue	whatever	jon	blah	blah	blah