And, because I'm always looking to practice my regex-fu, here's a version with all greedy matches, which tend to be faster--I timed a roughly 40% speed increase.

my %bits = $string =~ / ([^=]+)                  # Key
                        =<?                      # Seperator
                        ([^,>]+ (?> >[^,>]+)*)   # Value
                        >?(?:,\s*|\s*$)          # Termination
                      /gx;
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