Anyway, I would enable debugging on the Net::LDAP object and see what is being send and received by the script:

$ldap->debug(12);
[download]

Thank you for a tip.

Searching for uids less than 1000 and gt 500... Net::LDAP=HASH(0x22d4e
+e0) sending:
0000   82: SEQUENCE {
0002    1:   INTEGER = 2
0005   77:   [APPLICATION 3] {
0007   39:     STRING = 'ou=slurm,dc=lomonosov,dc=parallel,dc=ru'
0030    1:     ENUM = 2
0033    1:     ENUM = 2
0036    1:     INTEGER = 0
0039    1:     INTEGER = 0
003C    1:     BOOLEAN = FALSE
003F   17:     [CONTEXT 6] {
0041    9:       STRING = 'uidNumber'
004C    4:       STRING = '1000'
0052     :     }
0052    0:     SEQUENCE {
0054     :     }
0054     :   }
0054     : }
Net::LDAP=HASH(0x22d4ee0) received:
0000   12: SEQUENCE {
0002    1:   INTEGER = 2
0005    7:   [APPLICATION 5] {
0007    1:     ENUM = 0
000A    0:     STRING = ''
000C    0:     STRING = ''
000E     :   }
000E     : }
Ok
Found:
[download]

I suppose that 'context 6' in this context means 'less or equal'; according to rfc,

        LDAPMessage ::= SEQUENCE {
             messageID       MessageID,
             protocolOp      CHOICE {
                  bindRequest           BindRequest,
                  bindResponse          BindResponse,
                  unbindRequest         UnbindRequest,
                  searchRequest         SearchRequest,
                  searchResEntry        SearchResultEntry,
                  searchResDone         SearchResultDone,
[...]
        SearchRequest ::= [APPLICATION 3] SEQUENCE {
             baseObject      LDAPDN,
             scope           ENUMERATED {
                  baseObject              (0),
                  singleLevel             (1),
                  wholeSubtree            (2),
                  ...  },
             derefAliases    ENUMERATED {
                  neverDerefAliases       (0),
                  derefInSearching        (1),
                  derefFindingBaseObj     (2),
                  derefAlways             (3) },
             sizeLimit       INTEGER (0 ..  maxInt),
             timeLimit       INTEGER (0 ..  maxInt),
             typesOnly       BOOLEAN,
             filter          Filter,
             attributes      AttributeSelection }
[...]
        Filter ::= CHOICE {
[...]
             greaterOrEqual  [5] AttributeValueAssertion,
             lessOrEqual     [6] AttributeValueAssertion,
[...]
        AttributeValueAssertion ::= SEQUENCE {
             attributeDesc   AttributeDescription,
             assertionValue  AssertionValue }

        AttributeDescription ::= LDAPString
                                -- Constrained to <attributedescriptio
+n>
                                -- [RFC4512]

        AssertionValue ::= OCTET STRING
[download]

Everything seems to be OK, but *why* console utility 'ldapsearch' returns ~200 entries, and Net::LDAP doesn't?

answer has been found, thank you.

What was the issue? Inquiring minds want to know. Adding information as to the source of the problem, solutions tried, and one that actually worked will help those who come after you.

--MidLifeXis

Net::LDAP::Gateway contains a sample LDAP server that can dump the packets it receives as almost-human-friendly Perl data structures. It has served me in the past to compare and validate requests made through Net::LDAP and ldapsearch and solve problems as the one you were facing.