I'd like to see what Data::Dumper says is in your hash. What you have written has typos or is plain wrong. Just adding parentheses around the data yields a hash with only two keys. Do you mean to have an AoH? If so, enclose the sets of distinct data in curlies to get a hash ref in each slot and make the named structure an array. That will make the most sense for sorting, too.

Here's what I think you wanted,

my @fetch = (
    { sse_date => 4934056723, bld_num => '7.3.998.0.0' },
    { sse_date => 4934099999, bld_num => '7.3.1003.0.0' },
    { sse_date => 4949999999, bld_num => '7.3.1089.0.0' },
    #  . . .  etc. etc.
);
my @sorted_fetch = sort {
    $b->{'sse_date'} <=> $a->{'sse_date')
} @fetch;
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Your bld_num fields were in danger of becoming deprecated v-strings, so I quoted them.