Simple Perl Test

#!bin/perl -w

sub identifyTax($)
{
    my ($transactions) = @_;

    my $fee = 5;
    my $maximumTocalculateTax = 100;
    my $minimumTransactionsPerMonth = 3;
    my $numberOfMonthsToChargeFee = 0;

    foreach my $date (keys %{$transactions})
    {
        $_ = $date;

        my $currentMonth = $1 if m/\-(\d{2})\-/;
        my $numberOfTransactionsForCurrentMonth = 0;
        my $numberOfTransactionsWithinTheSameMonthAbove100 = 0;
        my $chargeFeeInThisMonth = 0;

        foreach my $date (keys %{$transactions})
        {
            $_ = $date;

            my $monthToCheck = $1 if m/\-(\d{2})\-/;

            $numberOfTransactionsForCurrentMonth++
                if $monthToCheck eq $currentMonth;

            $numberOfTransactionsWithinTheSameMonthAbove100++
                if $transactions->{$date} >= 100;

        }

        if ($numberOfTransactionsForCurrentMonth >= 1 && $numberOfTransactionsWithinTheSameMonthAbove100 >= 3)
        {
            $chargeFeeInThisMonth = 1;
        }

        $numberOfMonthsToChargeFee++ if $chargeFeeInThisMonth == 1;
    }

    return $numberOfMonthsToChargeFee * $fee;

}

sub sumTransactions($)
{
    my ($transactions) = @_;
    my $totalBalance = 0;

    foreach my $date (keys %{$transactions})
    {
        $totalBalance += $transactions->{$date};
    }

    return $totalBalance;
}

my $transactionsArrayRef =  [100, 100, 100, -10];
my $transactionDatesArrayRef =  ['2020-12-31', '2020-12-22', '2020-12-03', '2020-12-29'];


my %transactions;
@transactions{@{$transactionDatesArrayRef}} = @{$transactionsArrayRef};

my $tax = identifyTax(\%transactions);
my $totalBalance = sumTransactions(\%transactions);

$totalBalance -= $tax;
print "total balance " . $totalBalance;