as Fletch pointed out a '.Z' extention generally denotes a file that was compressed with the utility compress. Unfortunately modules that use Compress::Zlib will not work on .Z compress files (The compress utility is old and bascially deprecated). Your best option comes from the Compress:Zlib FAQ

Best Option:
If you have a newer version of the gzip (GNU zip) utility.

use Archive::Tar;

# using the cli utility gunzip 
# -c causes the file to be 'cat'ed
open F, "gunzip -c $filename |";

my $tar = Archive::Tar->new(*F);
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Other Option:
Get the ncompress utility and compile. Then you can:

use Archive::Tar;

# using the cli utility compress 
# -c causes the file to be 'cat'ed
open F, "uncompress -c $filename |";
# or use 
# open F, "zcat -c $filename |";

my $tar = Archive::Tar->new(*F);
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Archive::TarGzip does not seem to support .Z compressed files either.