As a thought (untested code ahead):

chdir 'D:\COLD\DULS';
my @all_files = glob('*');
my @cold_suff = grep(/^cold/,@all_files);
my @hot_suff = grep(!/^cold/,@all_files);

## do stuff wth hot and cold running data streams.
[download]

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i had a memory leak once, and it ruined my favorite shirt.