Properl Perl execution

Better yet, don't use system or exec in perl at all -- use internals

Don't use ls, use fileglobs, stat, and friends.
Don't use nc, use IO::Socket.
Don't use md5sum, use Digest::MD5.
Don't use /usr/sbin/sendmail, use Net::SMTP, etc.
etc, etc, etc.

If you want to specify argv[0] ($0 in perl) then use
   exec { "/bin/gzip" } "gunzip", "file.gz";

More helpful open and IPC hints in 

   perldoc perlopen
   perldoc perlipc