Though we have arrived at very similar solutions, I think yours fails to pick up multiple values for the last key: 
use strict;
use warnings;
use Data::Dumper;

my $data="key1=value1 key2=value2 value3 key3=value4 value5 value6 key
+4=value7 key5=value8 key6=value9 value10";

# Albannach version
my %hash;
while ($data =~ /(\w+=)((\w+( |$)+)+)/g) {
  $hash{$1} = $2;
}
print Dumper \%hash;

# gumpu version:
my %foo;
while ($data =~ m/(\S+)=(\S+($|([^=]+\s+)+))/g) {
  $foo{$1}=$2;
}
print Dumper \%foo;

[download]
Produces: 
$VAR1 = {
          'key4=' => 'value7 ',
          'key5=' => 'value8 ',
          'key1=' => 'value1 ',
          'key6=' => 'value9 value10',
          'key2=' => 'value2 value3 ',
          'key3=' => 'value4 value5 value6 '
        };
$VAR1 = {
          'key1' => 'value1 ',
          'key2' => 'value2 value3 ',
          'key3' => 'value4 value5 value6 ',
          'key4' => 'value7 ',
          'key5' => 'value8 ',
          'key6' => 'value9 '
        };

[download]

Update: The = in the key? You are right of course - silly me! Thanks gumpu!

--
I'd like to be able to assign to an luser

In reply to Re: Re: Parsing Challenge by Albannach
in thread Parsing Challenge by symŽ

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.