I think it's much clearer _without_ the quotes. Any valid bareword will be interpreted as a string, so why not use that? Same goes for => - I don't use quotes if it being a string is obvious.

Always using quotes might make you forget about words being interpreted as strings, and you might end up using $foo{function} where you meant to use $foo{+function} / $foo{function()}.

But as _always_, style is what YOU choose. (Just remember some common style issues so others will be able to read your code :)

2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$
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