I agree with all the comments from Tanktalus. I will add some info that could also be useful.

- Why calling shell commands? Unless speed is really an issue, Archive::Tar is quite handy and it is a core module. The same could be applied to md5 calculations, which could be made using Digest::MD5 (also a core module).

- There's a nice module IPC::System::Simple that handles very well all the system and exec calls, taking good care of edge cases, portability and return values, dying on error.

- For quick date formating, I always do the following:

use POSIX qw/strftime/;
$date = strftime( '%Y%m%d', localtime time );
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Good luck!