Using strict and warnings would certainly make your life (as a programmer) a little bit easier:

use strict;
use warnings;

while(<DATA>)
{
        chomp;
        my @pages = split(/\+\+/, $_);
        my @SonarData = ();
        my %DOWN = ();
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C:\src\perl\perlmonks\636961>perl -wc 636961.pl
"my" variable @pages masks earlier declaration in same scope at 636961
+.pl line 17.
String found where operator expected at 636961.pl line 220, near "$  p
+rint "@SonarData\n""
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Update: Your script is littered with small, but subtle errors that are easily detected using strict and warnings:

• A $ before print, probably just a typo.
• Redefined variables, "my" variable $total masks earlier declaration in same scope.
• Case errors: Global symbol "$endlevel" requires explicit package name.
• Wrong use of increment as pointed out by rhesa, would be reported by warnings: Useless use of array element in void context when $endlevel is corrected to $endLevel.

Once you get your script to do what you want, take a step back and consider refactoring (perl.com article).