Hash table key names with a minus

Rhodium has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Hash table key names with a by particle (Vicar) on Mar 24, 2002 at 15:18 UTC
barewords are not allowed. use quotes `$run{POWER-NODE} = "yes"` or `$run{'POWER-NODE'} = "yes"` ~Particle ;Þ	[reply] [d/l] [select]
Re: Re: Hash table key names with a by RMGir (Prior) on Mar 24, 2002 at 16:38 UTC
Normally, the {} would act as an implicit quote around your key. But `POWER-MODE` looks like a subtraction to the parser, so that messes things up. You'll have to quote it. -- Mike	[reply] [d/l]
Re: Hash table key names with a by Juerd (Abbot) on Mar 24, 2002 at 22:16 UTC
Valid unquoted strings, such as bare literal hash keys, consist of `\w` characters only. They are: A-Za-z0-9 and underscore (`_`). You can have leading or trailing whitespace, which can come in handy. Hoewever, the `-` character is not allowed, and forces it to be a normal expression. Without strict, it's allowed, because without strict it's allowed to use unquoted strings everywhere, not only in literal hash keys and the left operand of the `=>` operator. `# Assuming you don't have subs called POWER and/or NODE. no strict; $run{POWER-NODE} = yes; # equals: $run{ 'POWER' - 'NODE' } = 'yes'; # equals: $run{ 0 - 0 } = 'yes'; # and thus: $run{0} = 'yes';` [download] Consider: `$foo{99-24} = "Hello, world!\n"; print $foo{75};` [download] With strict, you can't use the unquoted strings `POWER`, `NODE` and `yes`. You'll have to add quotes as such: `$run{'POWER-NODE'} = 'yes'`. When you get rid of the `-`, and use an underscore instead, you can use an unquoted string after all (strict makes an exception for `=>`'s left operand, and for literal constant hash keys) like this: `$run{POWER_NODE} = 'yes'`. U28geW91IGNhbiBhbGwgcm90MTMgY W5kIHBhY2soKS4gQnV0IGRvIHlvdS ByZWNvZ25pc2UgQmFzZTY0IHdoZW4 geW91IHNlZSBpdD8gIC0tIEp1ZXJk	[reply] [d/l] [select]