Why does apt-cache search find packages which do not match the given regular expression?

I ran the following command at linux bash:

apt-cache search 'hex.*(view|edit)'

My intention was to find any software packages whose name/description contains the pattern 'hex.*(view|edit)'. But among the results I got this:

kipi-plugins - image manipulation/handling plugins for KIPI aware programs

How could this be in the results list? I didn't see any matching string in this result. Is this a bug of the apt-cache search command? Or do I mis-understand how the regular expression is used by this command?