print STDERR "This is line 1.\n";

my $var = STDERR;
print $var "This is line 2.\n";

my %hash = (key => STDERR);
print "The value of the hash variable is $hash{key}.\n";

my $which_stream = $hash{key};
print $which_stream "This is line 3.\n";

#print $hash{key} "This is line 4.\n";