The thing that surprises me though is that trying to increment the hash keys doesn't die like this one:
I agree, it seems odd. Consider:
my %h = (1 => 'Fred');
print "BEGIN fn()\n";
$_ = 'Barney';
print "-END- fn()\n";
12:02 >perl 541_SoPW.pl
The hash value is clearly aliased, since the assignment in sub fn persists in %h after the sub returns. But the hash key is not: it appears to be copied (passed by value), as $_ behaves as a variable local to sub fn. (Whereas a literal value like 42 or 'Wilma' is aliased, as evidenced by the Modification of a read-only value error message which results from trying to increment it or assign to it within the sub.)
An anomaly? Or a feature?
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