To send an e-mail to yourself, you should look into one of the many modules that exist to make this easy. I like MIME::Lite.

Update: Here is some (untested) code to work with. You will have to modify the email message with your e-mail addresses, and you might want to tweak the language of the Subject and Data (body text) to suit your style. Otherwise, the script reads the percent disk used from / and e-mails you if the percentage if greater than a threshold amount (in this case 90%)

#!/usr/bin/perl
                
use strict;
use warnings;
         
use Filesys::Df;
use MIME::Lite;

my $disk_info = df("/");
my $threshold = 90;
my $disk_percent;

if (defined($disk_info)){ 
      my $disk_percent = $disk_info->{per};
}

if ($disk_percent > $threshold) {

        my $message = MIME::Lite->new (
                From     =>'diskwatcher@yourcomputer.com',
                To       =>'fixitguy@othercomputer.com',
                Cc       =>'someonewhocares@somedomain.com',
                Subject  =>'ALERT: Im in ur disk usin ur inodes!',
                Data     => "It appears that the disk use threshold is
+ approaching the limit defined in your helpful script. You currently 
+have $disk_percent percent used.  Perhaps you should check on this."
               );
       
        $message -> send ;
}
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