> not ternary, just "binary",

yes it's binary.

> $var1 ?= die "ERROR: \$var1 already set." : $var2;

Thanks for demonstrating your use case, it's even stranger than I expected! ;-)

die will not return a value - actually it won't return at all.

> Maybe you'll see more elegant way how to do such thing.

Yes with a properly named custom-function operating on an alias.

something like 

 
sub init { 
   die "ERROR: \$var already set." if defined $_[0];
   $_[0] = $_[1];
}

init $var1 => 'value1';  # pretty elegant, right?
init $var2 => 'value2';
init $var3 => 'value3';

[download]

Please note the defined° , cause else wise you'd miss false values like 0 or "". (which renders your requirement for a new operator a bit useless)

UPDATE:

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery FootballPerl is like chess, only without the dice

°) a shorter way would have been $_[0] // die 'ERROR: ...';

Off by one, it's the inverted case :)

In reply to Re^3: RFC: "assignary" operator ?= : by LanX
in thread RFC: "assignary" operator ?= : by richard.sharpe

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