One that does not require the use of a fork:

#!c:/perl/bin/perl -w
$|++;

use strict;

sleep $ARGV[0] and exit if $ARGV[0];

eval {
  local $SIG{ALRM} = sub { die "timeout\n" };

  alarm 4; # change to timeout length
  system 'perl', $0, 6; # command to execute
  alarm 0;
};

warn "external command timed out: $@\n" if $@ eq "timeout\n";
print "continuing on, regardless of success/failure\n";
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