I'm guessing your problem is the use of `find dir_name -name *.tar`; together with tar -xf dir_name/$cnt ... since the find command will prepend all found *.tar files with dir_name, so, once expanded, your tar command is looking for dir_name/dir_name/<something>.tar.

Try

foreach $cnt(@count){
    system("tar -xf $cnt");
}
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or even

map { system("tar -xf $cnt") } @count;
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