or download this
sub sort_by_intf # sort interface alpha/number name mixture properly
{ my $A = $a; # just turn any number into a 0004 digit one
...
$B =~ s/([0-9]+)/ sprintf "%04d",9999-$1 /ge;
$B cmp $A; # reverse order happens to be useful here:
} # Tun0, Ser1, Port-channel2, Gi3, Fa4, Eth5