use constant DEBUG => 1;

debug("\$variable = $variable");

sub debug {
    return unless DEBUG >= 1;
    print 'DEBUG: ', @_, "\n";
}

##</code><code>##

sub debug {
    return unless DEBUG >= 1;
    print 'DEBUG: ',
        ( ref $_[0] eq 'CODE' ? $_[0]->() : @_ ),
        "\n";
}

##</code><code>##

debug( sub { Data::Dumper->new([$variable], ["variable"])->Dump } );