I'm not certain I understand your question with regard to "what is scalar?", but to do what you're attempting, you can use this:

my ($a, $b, $c, $d) = localtime(time);
print $d;
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After reading the first response to your question, what you were asking is clearer (had my blinders on, apparently). I like the way myocom explained it. In Perl, context is everything. I also like CheeseLord's snip of code better, if all you want is to grab the day of the month. My example is assuming you want to use other portions of the returned time and date as well.