Where is your code? If you want to submit a bug report, you should present a repeatable test case.

Anyway, there is no bug with that query. As the following snippet shows, the query you have proposed works just fine.

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use DBI;

my $user    = undef;
my $password= undef;
my $dbh=DBI->connect("dbi:mysql:test;host=localhost"
            . ";mysql_read_default_file=$ENV{HOME}/.my.cnf",
                $user,
                $password,
                {RaiseError => 1})
         or die "Can't connect: $DBI::errstr\n";


$dbh->do(qq{DROP TABLE IF EXISTS t}) ;
$dbh->do(qq{
    CREATE TABLE t (
        i int not null, 
        c char(10),
        primary key (i))
});
$dbh->do(qq{
    insert into t (i,c) values 
    (1, 'cat'),
    (2,'dog'),
    (3,'rabbit'),
    (4,'horse')
}) ;

my $query = q|SELECT * FROM t WHERE REPLACE(c,"","") REGEXP ?|;

my $sth = $dbh->prepare($query);
$sth->execute('t$');

print "one by one\n";
while (my $rec = $sth->fetchrow_arrayref()) {
    print Dumper($rec);
}

print "all at once\n";
print Dumper $dbh->selectall_arrayref($query,{ Slice=>{} }, '^d' );
one by one
$VAR1 = [
          1,
          'cat'
        ];
$VAR1 = [
          3,
          'rabbit'
        ];
all at once
$VAR1 = [
          {
            'c' => 'dog',
            'i' => 2
          }
        ];
[download]

Perhaps, you should consider a bug in YOUR code.

PEBCAK.