my $account_hash = $accounts->{78};

foreach my $transactions ($account_hash){
    
        push @{ $account_hash{ transactions } }, '-42.37';
    }

print Dumper $account_hash{ transactions };

##</code><code>##

A,01,Newton,Issac,Physics, 5.6      
B,144.56                            
B,1034.65                           
B,12.23                             
A,34,Einstein,Albert,Physics,12.22  
B,2346.89                           
B,876.23                            
B,7656.81                           
B,745.21                            
B,25.63                             
B,89.56                             
B,7789.23                           

##</code><code>##

%accounts = ( 
’78’ => { 
’surname’ => ’Feynman’, 
’firstname’ => ’Richard’, 
’job’ => ’Physics’, 
’balance’ => -17.34, 
’transactions => [ 7412.36, 2589.35, 95.32, 12.85, 789.68 ], 
}, 
’89’ => { 
’surname’ => ’Merx’, 
... 
}, 

##</code><code>##

use strict;
use warnings;
use Data::Dumper;
use Fatal qw/ open close / ;

my $data = "accounts.txt";

open (DAT, $data) or die "\"$data\" not existed or can't be opened!\n";
my @accounts;  
my @transactionamount;
my @fields1 = (
	 'Type',
	'member number', 
	'Surname',
	'Firstname',
	'Job', 
	'Balance',
	);
my @fields2 = qw/Type TransactionAmount/;
my $fields1;
my $fields2;
my $values;
while (<DAT>) {
    chomp;
    my @values = split(/,/);
    my %entry = map { $fields1[$_] => $values[$_] } ( 0..$#fields1 );
    #print Dumper %entry;
    
    if ($entry{"Type"} eq 'B'){
    	my %transactionamount = map { $fields2[$_] => $values[$_] } ( 0..$#fields2 );
    push @transactionamount, \%transactionamount;
  }
      else {
  	  push @accounts, \%entry;
}
}
print Dumper @transactionamount;