On the command line you could do,

tar -cvf newarchive.tar `tar -tf archive.tar | grep "gz" | grep -v "si
+g"`
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However, in your perl program, you could simply backtick to capture the ".gz" filename you want (using Perl's grep), and then pass that to system as the argument to the tar -cvf command. e.g.,

my @gzfiles = grep { m/gz/ && ! m/sig/ } `tar -tf archive.tar`
my @args = ( "tar","-cvf","newarchive.tar", @gzfiles );
system(@args) == 0 
    or die "Can't archive files: $!\n@gzfiles";
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