tie %ini_file, 'IniFiles', ( -file => "file1.txt");
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should be

tie %ini_file, 'Config::IniFiles', (-file => "file1.txt");
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Also, the line %$ini_sect = %{ $ini_file{$ini_sect} }; won't work under strict, since $ini_sect is a string and can't be used as a hash reference. But I'm assuming your code example is just a test and you'll be fixing that anyway.