our @GLOBAL_SYMBOLS; # these are not package constants, but Perl artifacts
BEGIN {
    @GLOBAL_SYMBOLS = qw(BEGIN EXPORT);
}

##</code><code>##

sub is_constant {
    my $k = shift;
   return $k =~ /^[A-Z]+$/ 
       && !grep { $_ eq $k } @GLOBAL_SYMBOLS
}

##</code><code>##

our %GLOBAL_SYMBOL; # these are not package constants, but Perl artifacts
BEGIN {
    %GLOBAL_SYMBOL = map { $_ => 1 } qw(BEGIN EXPORT ISA EXPORT_OK GLOBAL_SYMBOL);  
}

##</code><code>##

sub is_constant {
    my $k = shift;
   return $k =~ /^[A-Z_0-9]+$/
       && !$GLOBAL_SYMBOL{$k};
}