open(MYFILE, ">>$myfile") || die "Can't append to $myfile, Perl says $!";
flock(MYFILE, 2) || die "Can't lock $myfile, Perl says $!";
print MYFILE "Hello World!\n";
close MYFILE;

##</code><code>##

for ($i=0; defined($i); $i++){
    print "Help! I'm trapped in an infinite loop\n";
}

##</code><code>##

while (1) {
   print "foo";
}

# or you can write

for (;;) {
   print "foo"
}