Here is a sample LDAPSEARCH command to list CA ACF2 LOGONIDs which start with a specific character or group of characters.
Here's a sample LDAPSEARCH command to list LOGONIDs whose logonid starts with H (as an example).
ldapsearch -x -D cn=admuser -w admpswd -h hostname -p 389 -s one -b "acf2admingrp=lids,host=xxxx,o=yyy,c=zz" (acf2lid=H*).
If you wanted to check for a few characters you could change the value of ACFLID= to (for example) ACFLID=HIJ* - which will show all logonids that begin HIJ
You can see other sample ldapsearch commands for various cases in the pages for Sample CA LDAP Server Search Commands in the chapter for CAACF2_UTF Back-end in CA LDAP Server for z/OS Product Guide.