#!/usr/bin/perl
use strict;
use warnings;

my $delay = shift @ARGV || 1; # parameter
my $timeout = 3; # seconds
eval {
  ## Turn on timer.
  local $SIG{"__DIE__"};
  local $SIG{CHLD};
  local $SIG{ALRM} = sub { die "timed-out\n" };
  alarm $timeout;
  my $verylongprocess = `sleep $delay`;
  alarm 0; # disable alarm
};
die $@ if $@ eq "timed-out\n";
print "No timeout\n";
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it should cover external processes (hence, the 3 local SIG's). Not sure it works on Windows. But give it a try.

edit 2: Yes, it works, but instead of the unix "sleep" use the Windows "timeout" command (available in W7 and W10), like so:

  my $verylongprocess = `timeout $delay`;
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