I prefer the function strftime in POSIX for formatting dates. The only downside is that documentation for the format codes is "borrowed" from "C" and not included in perl's documentation.

use strict;
use warnings;
use POSIX 'strftime';
my $outfolder =
    strftime "Report_Output_%Y_%m_%d__%H_%M_%S", localtime();
print $outfolder;
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