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$|= 1;
my $next= time() + 60;
while( 1 ) {
...
    sleep $next-time();
    $next += 60;
}

use Time::HiRes;
$|= 1;
my( $next, $us )= gettimeofday();
...
    $next += 60;
    usleep tv_interval( [$next,$us], [gettimeofday()] );
}