use strict;
use warnings;

while(<DATA>)
{
    chomp;
    my $old = $_;
    s/\.(?=.*?\.)/_/g;
    print "Change: $old to $_\n";
}


__END__
test0.file0.new_20060411.zip
test1.file1.new_20060411.zip
test2.file2.new_20060411.zip
test3.file3.new_20060411.zip

##</code><code>##

Change: test0.file0.new_20060411.zip to test0_file0_new_20060411.zip
Change: test1.file1.new_20060411.zip to test1_file1_new_20060411.zip
Change: test2.file2.new_20060411.zip to test2_file2_new_20060411.zip
Change: test3.file3.new_20060411.zip to test3_file3_new_20060411.zip