But you simply don't need that: you can just die or warn in the usual way within your ternary operator, as you can see in the following Perl one-liners:

$ perl -e '$die_on_err=shift; 0 or ($die_on_err? die "failed\n" : warn
+ "warning\n")' 1
failed

$ perl -e '$die_on_err=shift; 0 or ($die_on_err? die "failed\n" : warn
+ "warning\n")' 0
warning
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I realize that; my error message is much longer than "failed", and I do not want to copy-and-paste it.

OK, I understand your motivations, now.

You still have numerous simpler ways to do it, such as storing your long error message in a variable (you actually had a $error variable in your original post) or doing something like this:

$ perl -e 'use diagnostics; $die_on_err=shift; 0 or print "error messa
+ge" and ($die_on_err? die $! : warn "\n" ) ' 0

error message
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or, yet simpler, using a subroutine such as the one proposed by Jenda in this post: Re: Take reference and then dereference die() and warn().