if($variable < $threshold) {
    my $command = '/usr/bin/blah';
    my $updatestring = << "EOF";
$variable is the value from DB.
$variable is less that $threshold
EOF

    my $UPDATE = `$command $updatestring`;
}
else {
    ...
}

##</code><code>##

open ( COMMAND, " $command $updatestring | ") or die $!;
while(<COMMAND>) {
     ....
}