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

my ( $number, %accounts );
while ( <DATA> ) {
    chomp;
    if ( /^A,/ ) {
        ( undef, $number, my @fields ) = split /,/, $_, -1;
        @{ $accounts{ $number } }{ qw/ surname firstname job balance /
+ } = @fields;
        }
    elsif ( /^B,/ ) {
        my $transaction = ( split /,/ )[ 1 ];
        push @{ $accounts{ $number }{ transactions } }, $transaction;
        }
    }


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

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

print Dumper $account_hash{ transactions };