Here's another way, but I can't say it's any less klutzy. There seems to be no way to avoid the use of some kind of operator for disambiguation.

use warnings;
use strict;

use constant STR   => 'a string';
use constant STREF => \'ref to a string';

print qq{one way '${ \STR }' and another '${ +STREF   }' \n};
print qq{and with another disambiguation '${  STREF() }' \n};
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Output:

c:\@Work\Perl\monks>perl constant_interpolation_1.pl
one way 'a string' and another 'ref to a string'
and with another disambiguation 'ref to a string'
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