$x = qq(odd number of items kaboom);
showvar('$x',\$x); # prints
# $x SCALAR, 1 ITEM:
#   'odd number of items kaboom'

@x = qw(odd number of items kaboom);
showvar('@x',\@x); # prints
# @x ARRAY, 5 ITEMS:
#   'odd'
#   'number'
#   'of'
#   'items'
#   'kaboom'

%x = qw(odd number of items kaboom);
showvar('%x',\%x); # prints
# %x HASH, 3 KEY/VALUE PAIRS: 
# kaboom => ***EMPTY*** 
#    odd => number  
#     of => items

sub showvar { # variables $, @, %
	local ($varname, $_) = @_;
	return print "\n*** One or two arguments are undefined ***\n" if !$_[0] or !$_[1];

	my $type = ref;
	return print "\nVariable '$varname' is inconsistent with its reference\n" if !$type;

	if   (/SCALAR/) {print "$varname $type, ";     show ($$_)}
	elsif (/ARRAY/) {print "$varname $type, ";     show (@$_)}
	elsif  (/HASH/) {print "$varname $type, "; showHASH (%$_)}
	else            {print "$varname $type, is not of type SCALAR/ARRAY/HASH\n"}
}

sub show {
	my $len = scalar @_;
	my $plural = $len>1 ? 'ITEMS' : 'ITEM';
	$_[0]="***EMPTY***" unless $_[0]; #avoid undef in mapping below
	print join "\n", "$len $plural:", map("  '$_'", @_), "------------\n\n";
}

sub showHASH {
	.
	.
	# Avoid length error if hash value undef
	$hash{$_} = '***EMPTY***' if !defined $hash{$_};
	.
	.
	# Pretty print
	print scalar keys %hash, " KEY/VALUE PAIRS: \n";
	.
	.
}