Your while loop is handling blocks, not lines in each block. One fix is:

#!/bin/perl

use strict;
use warnings;

local $/ = "END OF REPORT\n";

while  (<DATA>) {
    my @lines = split /\n/;

    for (@lines) {
        print if /\*\sparameters after change\s\=/ .. /\*\sNRG locatio
+n\s\=/;
    }
}

__DATA__
<13>Nov 13 17:27:25 OamCOMM[12260]:
TIMESTAMP=Tue Nov 13 17:27:25 2018

MSGCLS=OAMOPE
Title=OAM Create OPERATION
Severity=Inform
...
[download]

or just:

#!/bin/perl

use strict;
use warnings;

while  (<DATA>) {
    print if /\*\sparameters after change\s\=/ .. /\*\sNRG location\s\
+=/;
}

__DATA__
<13>Nov 13 17:27:25 OamCOMM[12260]:
TIMESTAMP=Tue Nov 13 17:27:25 2018

...
[download]