Test if multiple files exist

This solution seems to me more intuitive:

if [ `ls -1 /var/log/apache2/access.log.* 2>/dev/null | wc -l ` -gt 0 ];
then
    echo "ok"
else
    echo "ko"
fi

To avoid "too many arguments error", you need xargs. Unfortunately, test -f doesn't support multiple files. The following one-liner should work:

for i in /var/log/apache2/access.log.*; do test -f "$i" && echo "exists one or more files" && break; done

BTW, /var/log/apache2/access.log.* is called shell-globbing, not regexp, please check this: Confusion with shell-globbing wildcards and Regex.

If you wanted a list of files to process as a batch, as opposed to doing a separate action for each file, you could use find, store the results in a variable, and then check if the variable was not empty. For example, I use the following to compile all the .java files in a source directory.

SRC=`find src -name "*.java"`
if [ ! -z $SRC ]; then
    javac -classpath $CLASSPATH -d obj $SRC
    # stop if compilation fails
    if [ $? != 0 ]; then exit; fi
fi