or via POSIX:

#!/usr/local/bin/perl

use POSIX qw( sysconf _SC_OPEN_MAX );

$max = sysconf( &_SC_OPEN_MAX );
print "This process can have ",  $max, " open files\n";


# We all ready have STDIN, STDOUT, and STDERR open
$x = 3;

while( $x < $max ) {
   open( $x, "/etc/motd") ||
      die "cannot open file $!\n";
   $x++;
}

print "Should not have failed!\n";
print "Should fail now:\n";

open( $x, "/etc/motd" ) ||
  die "cannot open file $!\n";
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-derby