I'm not great with regexes but couldnt you do something like:

my %params = $raw =~ s/(\s+)\s*=\s*(\S+)/lc($1)/e while ($raw =~ s/(\s
++)\s*=\s*(\S+)/);
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Updated to say it won't work - the loop will never terminate:( You'd need to use /c and or\G or something somewhere, but I said I ain't good with regexes!