sprintf is the baby that you want to use - you will be able to read about that more in the documentation. But as date things are a very common use I'll repeat an example:

use strict;
use warnings;

my ( $day, $month, $year ) = (localtime)[3,4,5];

my $date = sprintf "%.04d%.02d%.02d", $year + 1900, $month + 1, $day;
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I'm sure this code has been shown thousands of time before

/J\