I am not quite sure I understood your question. Try this out..I think this kludge might be what you are looking for. 

use strict;
my %hash1 = (
    A => 5,
    B => 7,
    C => 2,
    D => 8,
);
my %hash2 = (
    1234 => "A,C",
    4567 => "A,B,D",
    5678 => "C",
);

my %hash3;

foreach my $key2 ( keys %hash2 )
{
    my %temphash = %hash1;
    foreach ( split /,/, $hash2{$key2} )
    {
        delete $temphash{$_};
        $hash3{$key2}= join ',', sort keys %temphash;
    }
}

foreach my $key ( keys %hash3 )
{
    print "$key : $hash3{$key}\n";
}

[download]

In reply to Re: How do I compare key from one hash with values from other? by 2501
in thread How do I compare key from one hash with values from other? by mug

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.