sub xfer_ssh {
    my ($xferSessionInfo, @other_args) = (@_);

    # set something in %xferSessionInfo - note use of the
    # -> operator to dereference.
    $xferSessionInfo->{foo} = "bar";

    # exactly the same thing, written a way that some find
    # easier to grok.
    ${ $xferSessionInfo }{foo} = "bar";

    return "ok";
}

my %xferSessionInfo;

&xfer_ssh(\%xferSessionInfo, @other_args);

print $xferSessionInfo{foo};   # prints "bar"