#!/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;
        }
    }

print Dumper \%accounts;

__DATA__
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
A,78,Feynman,Richard,Physics,-17.34
B,7412.36
B,2589.35
B,95.32
B,12.85
B,789.68