while(  <DATA>  ) {
    my @m= m{
      ^\s*
      (
        \w+
      | '(?:\\.|[^\\']+)*'
      | "(?:\\.|[^\\"]+)*"
      )
      \s*
      =>
      \s*
      (
        \w+
      | '(?:\\.|[^\\']+)*'
      | "(?:\\.|[^\\"]+)*"
      )
      \s*,?\s*$
    }x;
    print "(", join("|",@m), $/;
}
__END__
key => 44,
"key" => "fun. \"yes\" 'fun'",
'key' => 'yahoo\' "fun"'