Archived from the Transloadit support forum. Originally posted on April 4, 2014; details may be outdated, see our docs for current behavior. Original thread
Hello all,
Sounds that you need to update “Available operators for the conditions” in file-filter documentation ( https://transloadit.com/docs/conversion-robots#file-filter ) about !regex operator.
!regex is implemented but not documented 
best,
Francisco A