Nice work, LanX, thank you!
I tried that in a script, getting it to read all the lines of data, and it works perfectly!
Here it is: 
#!/usr/bin/perl

while (<DATA>)
{
        #($pre, $ranges) = split /=/, $_, 2;
        ($pre, $ranges, $value) = $_ =~ /^(.+?)=([^ ]+) (.+)$/;

        $del = "=";
        @keys = $pre;
        for $mult (split /:/, $ranges)
        {
                @keys = map { $a=$_; map { "$a$del$_" } split /,/, $mu
+lt } @keys;
                $del = ':';
        }
        #@hash{@keys} = ('value2') x @keys;
        @hash{@keys} = ($value) x @keys;
}

use Data::Dump 'dd'; dd \%hash;

__DATA__
Prefix1=A,B:c,d value1
Prefix2=A:b,c:1,2 value2
Prefix3=A:*:1,2 value3

[download]
And the output: 
{
  "Prefix1=A:c"   => "value1",
  "Prefix1=A:d"   => "value1",
  "Prefix1=B:c"   => "value1",
  "Prefix1=B:d"   => "value1",
  "Prefix2=A:b:1" => "value2",
  "Prefix2=A:b:2" => "value2",
  "Prefix2=A:c:1" => "value2",
  "Prefix2=A:c:2" => "value2",
  "Prefix3=A:*:1" => "value3",
  "Prefix3=A:*:2" => "value3",
}

[download]
If you have any suggested changes to my changes, I'm all ears.
I've also added 4 updates to my original post in case you're interested.  No worries if not. You can ignore update #1.

In reply to Re^2: Combinations of lists, etc by tel2
in thread Combinations of lists to a hash by tel2

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.