[BioC] how to exrtact col. names from exprs()

[S Peri]

Dear group, 
 
I have 50 CEL files. I have the expression values and
the colnames extracted as matrix files. The colnames
are named with the .cel file names. Now in a different
file the .CEL files are referenced to sample name. I
am interested in classifying the studies based on
samples. 
The other file looks like this:

XXXXXXXXX.CEL     xxKL_98
XXXXXxxxX.CEL     X2KL_98
XXXXXXXXX.CEL     X4KL_99
.....



Now in R my output looks like this:

> colnames(gliexp)[1:6]

[1] "XXXXXXXXX.CEL" "XXXXXXXXXXX.CEL" "XXXXXXXXXX.CEL"
"XXXXXXXXXXXXXXXX.CEL" "XXXXXXXXXXX.CEL"


I tried using grep function and it takes up only one
pattern. If I have to do this for whole study I would
have to do 150 times and I cannot do that. 
Is there some way similar to grep() or just grep()
itself where it takes more patterns.  where I can
define certain files (as patterns) as one go and
classiffy them as some category.  The file names are
unique with numbers and doe not seem to have specific
pattern. 

Please help me. 
thank you

Cheers
S