You could filter directly with the grep statement something like this

#!perl
use strict;
use Date::Calc qw(Today Add_Delta_YMD);

# calc dates
my $yesterday = sprintf "%4d%02d%02d",Add_Delta_YMD(Today(),0, 0,-1);
my $lastmonth = sprintf "%4d%02d%02d",Add_Delta_YMD(Today(),0,-1,-1);
print "Yesterday  : $yesterday\n";
print "Last Month : $lastmonth\n";

# path to folders
my $path = 'c:/temp';# or $DirCoolOut
opendir(D,$path) or die "Can't open the directory $path : $!\n";
my @folders = grep {/$yesterday|$lastmonth/} readdir(D);

for my $folder (@folders){
  print "Zipping folder $folder\n";
  # zip folders
  
}
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poj