I agree with my fellow monks who have already replied and might simply add a reference to Coping with Scoping for good measure.

For other clues as to why the author has used a block here, look at the immediately preceeding and following lines (which you have not yet shown us).

Finally, this line:

for ($i=0; $i<$armload_cnt; $i++){

suggests that the author is either not the most familiar with Perl or perhaps has translated this code from another language and the outer braces might simply be a residual figment of that. The more Perlish way to write this loop would be

for my $i (0 .. $armload_cnt - 1) {
[download]

Edit: fixed off-by-one in perlish loop (thanks AnomalousMonk for spotting). This is another reason IMHO why Perlish loops are superior - there's no need to inspect the operators inside the brackets so closely.