400 Regular expression too long

This error occurs when your regular expression exceeds 128 characters.

The Google Analytics API has a limit to the length of a regular expression, but there are workarounds. The API allows you to use multiple regular expressions separated by semi-colons or commas; each regular expression is limited to 128 characters, but the whole expression can be much longer.

See the section on combining filters in this document:

Google Analytics: API Filter Expressions