A possible brute force solution, because it turns out you only have to add "jql/" to the $uri. You better also remove startAt because of https://community.atlassian.com/forums/Jira-questions/POST-rest-api-3-search-jql-returns-400-quot-Invalid-request/qaq-p/3111234.

Oh, and by the way, search_accountId works differently. I logged https://rt.cpan.org/Public/Bug/Display.html?id=131856 for this. JIRA-Client-Automated is without a maintainer it seems.

#!/usr/bin/perl

use JIRA::Client::Automated;
package JIRA::Client::Automated;
sub search_accountId {
    my ($self, $emailAddress) = @_;
    my $uri = $self->{auth_url} .
        'user/search?query=' . $emailAddress . '&fields=accountId';
    my $request = GET $uri, Content_Type => 'application/json';
    my $response = $self->_perform_request($request);
    my $results = $self->{_json}->decode($response->decoded_content())
+;
    my $data_ref = @{$results}[0];
    die "something went wrong while searching for $emailAddress"
        if ($data_ref->{emailAddress} ne $emailAddress);
    return $data_ref->{accountId};
}

sub search_issues {
    my ($self, $jql, $start, $max, $fields) = @_;
 
        $fields ||= ['*navigable'];

    my $query = {
        jql        => $jql,
        #        startAt    => $start, # https://community.atlassian.c
+om/forums/Jira-questions/POST-rest-api-3-search-jql-returns-400-quot-
+Invalid-request/qaq-p/3111234
        maxResults => $max,
        fields     => $fields,
    };
    my $query_json = $self->{_json}->encode($query);
    my $uri        = "$self->{auth_url}search/jql/";

    my $request = POST $uri,
        Content_Type => 'application/json',
        Content      => $query_json;

    my $response = $self->_perform_request($request, {
        400 => sub { # pass-thru 400 responses for us to deal with bel
+ow
            my ($response, $request, $self) = @_;
            return $response;
        },
    });
 
    if ($response->code == 400) {
        my $error_msg = $self->{_json}->decode($response->decoded_cont
+ent());
        return { total => 0, errors => $error_msg->{errorMessages} };
    }
 
    my $results = $self->{_json}->decode($response->decoded_content())
+;
 
    return {
        total  => $$results{total},
        start  => $$results{startAt},
        max    => $$results{maxResults},
        issues => $$results{issues} };
}

package main;
...
[download]

Greetings, I hope someone might find this useful,

Thanks,

Johan