As dwildesnl suggested, reversing makes it significantly faster: see benchmark below. But don't do the optimisation unless you need it! 
my $data = <DATA>;

use Benchmark "cmpthese";
cmpthese(10_000, {

  "reversed" => sub { my %hash;
      my $reversed_data = reverse($data);
      $hash{reverse($2)} = reverse($1)
          while $reversed_data =~ /\s*([^=]+?)\s*=\s*(\w+)/g;
  },

  "non-reversed" => sub { my %hash; my $data = $data;
      $hash{$1} = $2 while $data =~ s/\s*(\w+)\s*=\s*([^=]+)$//;
  },

});

__DATA__
option1 = value0 value1 value2 option3 =value3 value4 option2=value5

[download]
gives results: 
                Rate non-reversed     reversed
non-reversed  1263/s           --         -89%
reversed     10989/s         770%           --

[download]

In reply to Re^2: Parsing named parameters by robin
in thread Parsing named parameters by sk

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