Just a thought, or a pointer, hope you dont mind.
Use references instead of a redundant join / split combination, that way if your data ever contains commas, it won't end in tears...
And ->arrayref is theoretically faster than ->array.
And you're using less variables up.

while (my $personref = $sth->fetchrow_arrayref()) {
    # take copy of data in array ref
    push @certified_people, \@{ $personref };
}
# stuff ..
for (@certified_people) {
    my ($fname,$lname,$sc_id) = @{ $_ };
    #stuff....
}
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