%{$datahash{"devinfo"}} = %devinfo;

##</code><code>##

$datahash{"devinfo"} = \%devinfo;

##</code><code>##

for (;;) {
 my %datahash;
 ..getdevicetopoll..
 ifpoll( \%datahash, $dev);
 print FILE dump %datahash;
}
...
sub ifpoll {
 my ($datahash, $dev) = @_;
 my %devinfo;
 my %interfaces; ## etc...
 ..snmp a lot of data here..
 $datahash->{"devinfo"} = \%devinfo;
 $datahash->{"interfaces"} = \%interfaces;
 return;
}