It seems to me that Ruby/Tk does not support multi-events sequence binding ?

on TCL/TK:
You could do :
bind . abc {puts stdout M}

on Perl/Tk:
You could bind like:
<Key-a><Key-b><Key-c> or <a><b><c>

on Ruby/TK:
Tk.root.bind( ' ??? ' ) { puts 'M' }

What to write on ??? place?
I try :
'abc' ==> no works.
'Key-aKey-bKey-c' ==> no works.  ( Ruby already take off the needs of <  > )
I try also
Tk.root.bind('Key-a', 'Key-b', 'Key-c') { puts 'M' }  ==> no works

So, does Ruby/Tk no support mutli-events sequence binding or
there is an other way to write it ?

Thanks.