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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(I prefer to allcap my globals.)