This works for me  (your sample file seems to be double-compressed, so it should more appropriately be named .txt.gz.gz): 

use IO::Uncompress::Gunzip qw(gunzip $GunzipError) ;

gunzip "2010-January.txt.gz" => "2010-January.tmp" or die "gunzip fail
+ed: $GunzipError\n";
gunzip "2010-January.tmp"    => "2010-January.txt" or die "gunzip fail
+ed: $GunzipError\n";

[download]

P.S. it's not XML, but rather classic mbox format.

In reply to Re: Reading gnu mailman archives by almut
in thread Reading gnu mailman archives by cormanaz

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