my $value = $hash{$key};

##</code><code>##

    my $value = $hash_ref->{$key};

##</code><code>##

sub mainCSV
{
	# Open the CSV input file
	open (my $infile_CSV1, '<', "$infile_CSV")
        or die "Unable to open $infile_CSV: $!\n";

	my %hash  = (); 
	
	while (my $line = <$infile_CSV1>) 
	{
		chomp;
		$line =~ s/\s*\z//;
		my @array_CSV = split /,/, $line;
		my $key_CSV = shift @array_CSV;
		push @{ $hash{$key_CSV} }, $_ foreach @array_CSV;
		print Data::Dumper->Dump([ \@array_CSV, \%hash], ["array_CSV", "hash"] );
	}
	
	# Explicit scalar context 
	my $size = scalar keys %hash; 
}

##</code><code>##

sub mainCSV
{
	# Open the CSV input file
	open (my $infile_CSV1, '<', "$infile_CSV")
        or die "Unable to open $infile_CSV: $!\n";

	my %hash  = (); 
	my $hash_ref = \%hash;
	
	while (my $line = <$infile_CSV1>) 
	{
		chomp;
		$line =~ s/\s*\z//;
		my @array_CSV = split /,/, $line;
		my $key_CSV = shift @array_CSV;
		push @{ $hash_ref->{$key_CSV} }, $_ foreach @array_CSV;
		print Data::Dumper->Dump([ \@array_CSV, $hash_ref], ["array_CSV", "hash_ref"] );
	}
	
	# Explicit scalar context 
	my $size = scalar keys %hash; 
	
}

##</code><code>##

sub mainCSV
{
	# Open the CSV input file
	open (my $infile_CSV1, '<', "$infile_CSV")
        or die "Unable to open $infile_CSV: $!\n";

	my $hash_ref = {};
	
	while (my $line = <$infile_CSV1>) 
	{
		chomp;
		$line =~ s/\s*\z//;
		my @array_CSV = split /,/, $line;
		my $key_CSV = shift @array_CSV;
		push @{ $hash_ref->{$key_CSV} }, $_ foreach @array_CSV;
		print Data::Dumper->Dump([ \@array_CSV, $hash_ref], ["array_CSV", "hash_ref"] );
	}
	
	# Explicit scalar context 
	my $size = scalar keys %$hash_ref; 
	
}