Can't reproduce the issue, i.e. it works fine for me without the debugger:

#!/usr/bin/perl -w
use strict;
use Getopt::Long::Descriptive;

my ($opt, $usage) = describe_options(
  'my-program %o <some-arg>',
  [ 'server|s=s', "the server to connect to"                  ],
  [ 'port|p=i',   "the port to connect to", { default => 79 } ],
  [],
  [ 'verbose|v',  "print extra stuff"            ],
  [ 'help',       "print usage message and exit" ],
);

print($usage->text), exit if $opt->help;
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$ ./877972.pl --help
my-program [-psv] [long options...] <some-arg>
    -s --server     the server to connect to
    -p --port       the port to connect to
                  
    -v --verbose    print extra stuff
    --help          print usage message and exit
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(tested with v5.10.1 (*) built for x86_64-linux-thread-multi)

Update: as the first problem happens here:

sub _validate_with {
  my (%arg) = validate(@_, {    # <-- line 442
    name   => 1,
    params => 1,
    spec   => 1,
    opts   => 1,
    usage  => 1,
  });
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and validate() is from Params::Validate, maybe there's some problem with this module? Which version are you using? (0.95 here)