c:\@Work\Perl\monks>perl -w -le
"use v5.10;
 say X;
 say $main::{X};
 if(exists $main::{X}    ){ say 'A: exists';} else {say 'A: does not exist';}
 if(exists $main{X}      ){ say 'B: exists';} else {say 'B: does not exist';}
 if(exists $main::main{X}){ say 'C: exists';} else {say 'C: does not exist';}
 die 'not the same' if \%main != \%main::main;
 die 'are the same' if \%main == \%main::;
 if( defined(X) ){say 'defined';} else {say 'not defined';}
"
say() on unopened filehandle X at -e line 1.
*main::X
A: exists
B: does not exist
C: does not exist
defined