i like the idea of requiring the user to add wildcards explicitly, but if you favor about backward compatibility, one suggestion would be to add " " when you want exact matches, so a search for lim would be (*lim*) but a search for "lim" would be (lim).. what do you think?

in this case:
lim and *lim* are the same
"lim" are exact matches
lim* are beginning with lim
*lim are ending with lim

we keep backwards compatibility and add the option to exact matches, in newer versions of deken you could put a hint "put quotes if you want exact matches! see the docs for more examples on wildcards usage"