As nothingmuch suggested:

sub ntohl
{
     pack("L", unpack("N", $_[0]));
}

sub ntohs
{
     pack("S", unpack("n", $_[0]));
}

sub htonl
{
     ntohl(@_);
}

sub htons
{
     ntohs(@_);
}
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Remember that on some systems there is no difference between "Network" and "Host" order. Using reverse is irresponsible.

This is all mostly irrelevant anyway, since standard modules like IO::Socket take care of it all for you automatically.