You can use alarm.  For your purposes, I'm assuming the result would look like this:

use strict;
use warnings;
 
my $timeout = 3;

eval {
    local $SIG{ALRM} = sub { die "alarm\n" };
    alarm $timeout;
    `perl -e "while(1) { }"`;
    alarm 0;
};

if ($@) {
   die "DID timeout after $timeout second(s)\n";
}

print "never see this text\n";
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