karl@rantanplan:~/src/myC$ touch nose
karl@rantanplan:~/src/myC$ find . -type f -mmin 1
./nose
karl@rantanplan:~/src/myC$ find . -type f -mmin 3 -exec rm -i {} \;
rm: remove regular empty file './nose'?
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Update: Add -size 0 for testing.

My point is where do i need to correct

where is the problem comes from

How i can delete those files which are 30minutes older

based on my script, not bash, or command line. your example are really confusing

for my $file(@$folder) {
        my $time = (stat($file))[9];
        my $mod_time = strftime('%M', localtime($time));
        if ($mod_time > '30') {
            unlink glob "$folder/*.sql";
        }
        }
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What do you think this line does:

        my $mod_time = strftime('%M', localtime($time));
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Compare this with the documentation of POSIX::strftime and localtime. Tell us where the documentation supports your interpretation.