select ...
where  ...
OR mdf_20 LIKE '_a4bbf326102e3064a8d9e06558c4b5e2020ee353HASH(0x826998)'
                                                         ^^^^^^^^^^^^^^

##</code><code>##

select ...
where  ...
OR mdf_20 LIKE '''_a4bbf326102e3064a8d9e06558c4b5e2020ee353HASH(0x826998)'''
                ^^                                         ^^^^^^^^^^^^^^^^

##</code><code>##

$sql = "SELECT action_id
  FROM transactions LEFT JOIN actions 
      ON transactions.transaction_id = actions.transaction_id
    LEFT JOIN merchants ON merchant_id = idmerchants
  WHERE mdf_20 = ? 
    AND action_type IN ('capture','sale')
    AND ABS(amount) = ABS(?) AND success = 1 
    AND processor_settlement_date IS NULL
    ORDER BY transaction_date;";
my $sth = $dbh->prepare($sql);
$sth->bind_param(1, '1442a29888840b0b9505d34da6cd8897d153976d');
$sth->bind_param(2, 49.95);
$sth->execute;
my $aref = $sth->fetchrow_array if (defined $aref);
print join(', ', @$aref),"\n";
$sth->bind_param(1, 'a4bbf326102e3064a8d9e06558c4b5e2020ee353');
$sth->bind_param(2, 4.95);
$sth->execute;
$aref = $sth->fetchrow_array;
print join(', ', @$aref),"\n";
$sth->finish;

my $like_cond = '';
$sql  = "SELECT action_id,transaction_date FROM profitorius.actions 
  WHERE transaction_id LIKE ? 
    AND ABS(amount) = ABS(?) AND success = 1 
    AND action_type IN ('capture','sale')
    AND processor_settlement_date IS NULL
    ORDER BY transaction_date;";
$sth = $dbh->prepare($sql);
$like_cond = '1442a29888840b0b9505d34da6cd8897d153976d%';
$sth->bind_param(1,$like_cond);
$sth->bind_param(2, 49.95);
$sth->execute;
$aref = $sth->fetchrow_array;
print join(', ', @$aref),"\n";

$like_cond = 'a4bbf326102e3064a8d9e06558c4b5e2020ee353%';
$sth->bind_param(1,$like_cond);
$sth->bind_param(2, 4.95);
$sth->execute;
$aref = $sth->fetchrow_array;
print join(', ', @$aref),"\n";