Another solution is to declare @array in the main program and pass a reference to &TieVariable.

TieVariable(\my @array); ### Pos1
print "### Initialization finished\n";
for (0..$#array) {
   print "$_: $array[$_]\n";
} # for
$array[6] = 1000;

untie @array;

sub TieVariable {
   my $array = shift;
   tie @$array, 'Tie::Excel::Array';
   $array->[$_] = 5 * $_ for 0..5;
}
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You can get rid of then need for the backlash at Pos1 by giving TieVariable a prototype, but I would not recommend it.