OK, that's the code. But what do you expect from us now?

Did you check, what toolic and me already suggested?

Do you still have problems? What kind of problems? What happens when you execute the script? What do you want to happen?

At least, my %files(); causes an syntax error.

You still don't check whether mkdir is successful or not.

I just rewrote your script to get it syntactically OK. I think there is more optimization possible.
I don't know, if it does what you want, but you might get the idea, what I meant with my previous comments.

#! /usr/bin/perl
use strict;
use warnings;

use DateTime;
use File::Copy;
use File::Find;
use File::stat;
use Time::localtime;
use File::Spec::Functions qw( catdir catfile );

my $now        = DateTime->now( time_zone => 'floating' );
my $yesterday  = $now->substract( days => 1 );
my $year       = $yesterday->year;
my $month      = $yesterday->month;
my $month_abbr = uc( $yesterday->month_abbr );
my $day        = $yesterday->day;
my $year_abbr  = substr $year, 2, 2;
my $mdy        = $now->strftime( "%m-%d-%y" );

print "$year\t$year_abbr\t$month\t$month_abbr\t$day\n";

my $basedir = '/Users/mgavi.brathwaite/Desktop/BioinfDev/SequenceAssem
+blyProject';

my $root     = catdir( $basedir, "Sequencing_Results/Results $year/New
+ Version/Amanda Li/$month_abbr" ); 
my $komp_dir = catdir( $basedir, 'KOMP' );


#> sub routines
#> ------------------------------------------------------------


sub wanted {
    
    # return if current filename ends with 'xls'
    return        if $File::Find::name  =~ m/xls\z/;
    # return if file is younger than 1 day
    return        if -M $File::Find::name > 1.0;

    # determine maid number
    if ( my ( $maid ) = $File::Find::name =~ m{/(\d*)} ) {
        # store full path to file if maid number could be determined; 
+see: "perldoc perldsc", Hashes of Arrays
        push @{ $files{$maid} }, $File::Find::name;
    }

}


sub maid_dirs {
    
    my ( $maid ) = @_;
    my @dirs     = glob( catfile( $komp_dir, '*' ) );

    for my $dir ( @dirs ) {
        return $dir if -d $dir and $dir =~ m{/$maid\D};
    }

    # if no suitable dir was found
    return undef;
}


#> main script
#> ------------------------------------------------------------


# determine files
my %files;
find( \&wanted, $root );


for my $maid ( keys %files ) {

    my @files = @{ $files{$maid} };

    next if @files != 4;

    if ( my $dest_dir = maid_dirs( $maid ) ) {

        my $directory = catdir( $dest_dir, 'sequencing' );
        mkdir( $directory, 0755 ) or die "mkdir failed: $!\n";

        for my $file ( @files ) {
            copy( $file, catfile( $directory, $file ) ) or die "copy f
+ailed: $!\n";
        }
    }
}

print "Job done\n";
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