You can simply pass the $sock to the subroutine and my it.. Its already a ref to a filehandle, hence you can work with it just like you are proposing... Here is a simple snippet to test sendmail on the local machine...

use strict;
use IO::Socket;

my $sock = IO::Socket::INET->new(
   PeerAddr => '127.0.0.1',
   PeerPort => '25',
   Proto    => 'tcp',
   Type     => SOCK_STREAM
);

do_mail($sock);
print $sock "quit\n";
close($sock);

sub do_mail {
   my($handle) = shift;

   my $buf = <$handle>;

   print "Sendmail ", $buf ? "is OK\n" : "is not responding\n";

}
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See? no alterations need to be made and the handles name is local to the sub routine.. the actual handle is still global I believe in this case, so I wouldnt suggest trying to have multiple sub routines reading the same handle at the same time..


/* And the Creator, against his better judgement, wrote man.c */