my @filenames = glob '/tmp/dir1/d1*';

my @files_and_sizes;
for my $filename (@filenames) {
    my $filesize = -s $filename;
    push @files_and_sizes, [$filename, $filesize];
}

use Data::Dumper;                # just for demo & debugging
print Dumper \@files_and_sizes;  # just for demo & debugging

@files_and_sizes = sort { $$b[1] <=> $$a[1] } @files_and_sizes;

print Dumper \@files_and_sizes;  # just for demo & debugging

my $var1 = $files_and_sizes[0][0];

print $var1;