Re-read the docs for File::Find. The return value of wanted is discarded. It's definitely not returned by find.

Replace

my %fileInfo = find(...);

sub wanted {
   ...
   $fileInfo{$fileName} = $fileName;
   return %fileInfo;
}
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with

my %fileInfo;

find(...);

sub wanted {
   ...
   $fileInfo{$fileName} = $fileName;
}
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Actually, I'm not sure why you are using a hash.

my @fileNames;

find(...);

sub wanted {
   ...
   push @fileNames, $fileName;
}
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By the way, please use <c>...</c> tags around code posted to PerlMonks.

Update: Original post (follows behind readmore) was junk. I latched onto the wrong problem.

I'm guessing this is using File::Find, right?. The first problem is you're assigning to %fileInfo the return value of find, not wanted. The second problem, is deep within the guts of File::Find, the return value of wanted is just discarded anyways. This is one of the limited times that you're better off using a global

#!/usr/bin/perl

use strict;
use warnings;

use File::Find;
use var qw( $FILEINFO );

find( \&wanted, @directories );

sub wanted {
  if (!(-d)) {
    my $fileName = $File::Find::name;
    $fileName =~ s/\//\\/g;
    my $fileSize = ( -s $fileName);
    if (!(exists $FILEINFO{$fileName})){
      $FILEINFO{$fileName} = $fileName;
      print "$FILEINFO{$fileName}\n";
    }
  }
}
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In File::Find::Closures I have a bunch of examples of using closures to provide the wanted subroutine for find and then reporting the results later.