from my examples here, I summise that the tertiary conditional is an if statement(term/expression), wrapped in a do block. Is this the case?

B::Concise may reveal if they resolve to the same opcodes ... if they're the same :)

shotgun

Ternary operator (there's no Trinary operator ), To Trinary or not to Ternary, (mini-if ternary), Re^2: Two simple code style advice questions (tye), ternary operator as lvalue failing to induce evaluation of right-hand expression in list context
Multiple if-else statements using C-style ternary operator
Perl ternary operator style
Question about ternary operator