my %groups = map{
	open my $fh, '>', "Group$_" or die $!;
	$_ => $fh;
} qw[ABC DEF ...];

for my $empNo (keys %emp) {
	for my $grp (keys %groups) {
		#! Note the {} (bare block) around the filehandle are necessary.
		print { $groups{$grp} } $emp{$empNo}{Emp} if $emp{$empNo}{Org} =~ m[$grp];
	}
}