First of all, please use  <code> ... </code> tags as advised in Writeup Formatting Tips and Markup in the Monastery. To fix your OP, please see How do I change/delete my post?

I don't know what is "$test -> {'RecordType'} = UNKNOWN;".

$test is a hash (or associative array) reference.
$test->{'RecordType'} accesses a key of the hash that is referenced.
$test->{'RecordType'} = UNKNOWN; assigns a value to a key of the hash. Unfortunately, it seems as if the bareword  UNKNOWN is being assigned, which has no value. This error would have been caught if the statement
    use strict;
had been placed at the beginning of the code.

c:\@Work\Perl\monks>perl -le
"use warnings;
 use strict;
 ;;
 use Data::Dumper;
 ;;
 my $test;
 ;;
 $test->{'RecordType'} = 'UNKNOWN';
 ;;
 print Dumper $test;
"
$VAR1 = {
          'RecordType' => 'UNKNOWN'
        };
[download]

Please consider these points and we can go forward from here. (Update: Actually, these seem like pretty basic questions, so maybe take a look at perlintro and some of the articles in Getting Started with Perl first.)

#!/usr/bin/perl
use strict;
use warnings;
use constant {KNOWN => 1, UNKNOWN => 0};

my $test;
$test -> {'RecordType'} = UNKNOWN;

#case 1
if($test ->{'RecordType'}){ # if $tset->{'RecordType'} == any 'true' v
+alue, i.e 1
    print "case1 is known\n";
}
else {
    print "case1 is unknown\n"; 
}

#case 2
if($test ->{'RecordType'} == KNOWN){ # if $tset->{'RecordType'} == 1
    print "case2 is known\n";
}
else {
    print "case2 is unknown\n";
}
[download]

case1 is unknown
case2 is unknown
[download]

Constants are usually used to make code more clear (names instead of numbers).

Constants are explained here.

As a token of your gratitude, please consider editing (How do I change/delete my post?) your original post to fix the  <code> tags and make the post readable.

---

Give a man a fish:  <%-{-{-{-<