#!/usr/bin/perl
use strict;
use warnings;
use File::stat;
use POSIX qw(strftime);

my $dbhost = '';
my $dbuser = '';
my $dbname = '';  
my $folder = 'backup/';  
my $filename = join '.', 'db.backup', time, 'sql';

if ($bp = `mysqldump --host=$dbhost --user=$dbuser --password="dbpassword" $dbname > $folder$filename`) {

    for my $file(@$folder) {
        my $time = (stat($file))[9];
        my $mod_time = strftime('%M', localtime($time));
        if ($mod_time > '30') {
            unlink glob "$folder/*.sql";
        }
    }
} else {
    die "error";
}