use Regexp::Common;

my $re = qr/
    ( \w+ | $RE{quoted} )
    \s+ => \s+
    ( \w+ | $RE{quoted} )
    ,?
/x;

/$re/ and print "$1: $2\n" while <DATA>;

__DATA__
key => 44,
"key" => "fun. \"yes\" 'fun'",
'key' => 'yahoo\' "fun"'