It is quite interesting to see that sometimes mistyping can lead to unexpected discoveries in the language syntax...

Surprisingly, I couldn't find anything about this syntax in Perl or C on the Net... But from (working, heh) code, it seems that an empty condition is evaluated as true...

Here's what I found that might be related. It's from description of perl5db, the Perl debugger:

...

%postponed

Saves breakpoints for code that hasn't been compiled yet. Keys are sub
+routine names, values are:

    * compile - break when this sub is compiled
    * break +0 if <condition> - break (conditionally) at the start of 
+this routine. The condition will be '1' if no condition was specified
+.

...
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