% perl5005 -e 'require 5.6'
Perl 5.6 required--this is only version 5.00503, stopped at -e line 1.

% perl56 -e 'require 5.6'
Perl v5.600.0 required--this is only v5.6.0, stopped (did you mean v5.6.0?) at -e line 1.

% perl56 -e 'require 5.6.0'

% perl5005 -e 'require 5.6.0'
Can't locate 5.60 in @INC (@INC contains: /usr/lib/perl5/5.00503/i386-linux /usr/lib/perl5/5.00503 /usr/lib/perl5/site_perl/5.005/i386-linux /usr/lib/perl5/site_perl/5.005 .) at -e line 1.

% perl5005 -e 'require 5.006'
Perl 5.006 required--this is only version 5.00503, stopped at -e line 1.

% perl56 -e 'require 5.006'

%