I'm not sure what is going on here.
Prepare the statement before starting the loop (do it only once)
Execute the statement, filling in the placeholder (?) within the loop

my $addr_lookup = 
    'SELECT u2addr.id FROM u2addr WHERE u2addr.addr = ?';
my $stm = $dbh->prepare($addr_lookup);

foreach my $addr (@addr)
{

    $stm->execute($addr);
    
    my @results=();
    
    while (my @row = $stm->fetchrow_array)
    {
        push (@results, [@row]); #push array ref to @row
                                 #using new memory and copy of @row
                                 #could also just fetchrow_arrayref
    }
    
    ## do something with @results here...
    ## perhaps: "print Dumper \@results;"
    ## to see what you have in @results?
}
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