<?php

$profiler = new ExcimerProfiler;
$profiler->setPeriod( 0.001 ); // every 1ms
$profiler->setEventType( EXCIMER_CPU );
$profiler->start();
register_shutdown_function( function () use ( $profiler ) {
	$profiler->stop();
	file_put_contents('trace.log', $profiler->getLog()->formatCollapsed() );
} );

KrinkleMac in ~/Development/less.php
$ docker run -it --rm --entrypoint /bin/bash --volume $PWD:$PWD docker-registry.wikimedia.org/releng/php81:0.2.0
…
nobody:/less.php# php -d auto_prepend_file=excimer2trace.php bin/lessc test/Fixtures/bootstrap-3.2/less/bootstrap.less out.css