This same error is discussed in this thread.
Ripping arturo's post this is the solution (read it for more detail).

perldoc:perldiag tells us about this error:
Can't ignore signal CHLD, forcing to default
(W signal) Perl has detected that it is being run with the SIGCHLD signal (sometimes known as SIGCLD) disabled. Since disabling this signal will interfere with proper determination of exit status of child processes, Perl has reset the signal to its default value. This situation typically indicates that the parent program under which Perl may be running (e.g. cron) is being very careless.

The solution:

#!/usr/bin/perl -w
use strict;
BEGIN {
  SIG{CHLD} = 'DEFAULT';
}
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