My question is: how is the expression in $hash{expression} stringified?

Same as everywhere else.

• A number stringifies to a string representing that number. The exact format is not specified and could very well be platform-dependent. Use sprintf to get more control.
• undef stringifies to the NUL (0-length) string (and issues a warning).
• Objects of classes that overload stringification can stringify however they like.
• Compiled regexs stringify into the source regexp.
• Blessed references get stringified to some unique opaque value. (For example, Class=REFTYPE(0xADDRESS))
• References get stringified to some unique opaque value. (For example, REFTYPE(0xADDRESS))

I think that's all the scalar subtypes?

You can force stringification a number of ways, including

"$var"
[download]

and

'' . EXPR
[download]

The form of the expression I was trying to understand was $href->{$x,$y}

$href->{$x,$y} is rarely used and probably shouldn't be used. I think the only reason it exists is for backwards compatibility with very old Perls. I agree that it should be mentioned in perldata.

Also, how should I, if I were so bold, suggest an improvement to the standard documentation?

perlbug

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