It's an unusual requirement for sure (homework?) but taking you at your word:

use strict;
use warnings;

use Test::More tests => 2;

my @rec = (
    {
        have => 'ABC;123;;;;;HELLO;',
        want => 'ABC;"123";"";"";"";"";"HELLO";'
    },
    {
        have => 'DEF;345;;BANANA;12DEF;44,55;4*12;;;;;;;;3;',
        want => 'DEF;"345";"";"BANANA";"12DEF";"44,55";"4*12";"";"";""
+;"";"";"";"";"3";'
    }
);

for my $this (@rec) {
    $this->{have} =~ s/;/";"/g;
    $this->{have} =~ s/";/;/;
    $this->{have} =~ s/;"$/;/;
    is ($this->{have}, $this->{want})
}
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I have a sneaking suspicion that the goalposts may be about to move. Let's hope not.