Source

File: wp-includes/pomo/translations.php

function make_plural_form_function( $nplurals, $expression ) {
			try {
				$handler = new Plural_Forms( rtrim( $expression, ';' ) );
				return array( $handler, 'get' );
			} catch ( Exception $e ) {
				// Fall back to default plural-form function.
				return $this->make_plural_form_function( 2, 'n != 1' );
			}
		}