Something

#!/usr/bin/perl -w

&start_mem;
sub start_mem {
    sub mem {
        ($memsources = cat("/proc/meminfo")) =~tr/\n / /;
        $memsources =~/(\d+).*?(\d+).*?(\d+).*?(\d+)/;
        $memused = sprintf ("%.1f",($1 - $2 - $3 - $4)/1024);
        $memtotal = sprintf ("%.1f",($1/1024));
        $memper = sprintf ("%.f",($memused/$memtotal)*100);
        push @final, "Mem usage: $memused/$memtotal MB ($memper%)";
    }

    sub final {
        print "($memper%) $final \n";
    }
}