@hash{'a', 'b'}
                              $array[0]     $hash{'a'}
                           
           *glob     
                                               glob       

                       $$foo[1]       aka $foo->[1]
     * dereference     $$foo{bar}     aka $foo->{bar}
                       ${$$foo[1]}[2] aka $foo->[1]->[2]
                       ${$$foo[1]}[2] aka $foo->[1][2]
                     
                         
     
 ->                                 .
 

   ~ 
 =~ 
                         
           
 << >>    
         
 
                         for equals foreach (ALWAYS)
 &
 | ^              
                                             /i case insens.
                  $     str. end (before \n) /m line based ^$
    ...                                      /s . includes \n
 ?:                                          /x ign. wh.space
                                             /g global
   =>             {3,7} repeat in range
                                         
                  (?:)  no capture       .  == [^\n]
                  []    character clas 
                 
                  
                  \z    string end 

                    
                                                    
                                                    
                                                     
                                                     
                                                          
 
                                       
                                       
                                       $0    program name
                                       $/    input separator
                                       $\    output separator
                                       $|    autoflush
                                       $!    sys/libcall error
                                       $@    eval error
                                       $$    process ID
                                       $.    line number