The choice of making \ special inside single quotes was a design mistake. The only reason that anything needs to be special inside of single quotes is so that you can include the delimiter in the string. A much better way to do that would have been to allow two consecutive delimiters to be interpretted as one escaped delimiter. This is a common trick used a lot of places. It doesn't scale well in a lot of situations, but it would be perfect for Perl single-quoted strings.
'This isn\'t bad' # would become 'This isn''t bad' q(Too many \)s) # would become q(Too many ))s) q"You \"need\" this" # would become q"You ""need"" this"
The reason this would be a superior decision (and not just an alternative) is that it means that there is only one special character for each single quoted string, the delimiter. And since Perl allows balanced delimiters, the delimiter doesn't even need to be escaped much of the time.
Perl has such a nice, rich variety of quoting schemes that most any data you want to include can be written in a clean way. The one exception is backslashes that are special in all of the quoting schemes except for "here docs". But "here docs" are cumbersome for things other than several lines of text.
The fact that \ followed by anything other that \ or the delimiter causes the \ to be preserved in single-quoted strings helps aleviate this. It also causes confusion and bugs. People get in the habit of writing 'C:\temp\x.dat' and then don't realize why '\\host\share\dir' doesn't work and probably waste a lot of time trying to figure it out (or try 'C:\temp\').
I don't see a good way to change this, so it is just something to live with.
BTW, an example of how this scheme doesn't scale well is VMS. VMS's equivalent of shell script (or "batch" files) uses " to quote arguments and "" to include quotes in quoted strings. So if you want to write a script that wirtes a Makefile that passes an argument to the C compiler defining a string alias to the preprocessor, then you want the C compiler to see -Dname="val" so you have to put "-Dname-""val""" on its command line, which means you have to use """-Dname-""""val""""""" in your script. But Perl lets you use delimiters other than " and ' so this scaling problem doesn't apply in Perl. But I suspect this problem may have given this design "a bad name" and helped prevent it from being used when Perl was designed.
Update: Perhaps we should just add a qd() form of quoting that doesn't treat \ as special and requires a doubled delimiter to include it (unbalanced) into the string.
So, why isn't there a way to close a string early? Image the string 'Open delims are (, [, {, or <' and trying to use q(), q[], q{}, or q<> with it.
Update 2: Ah, I've stumbled across an advantage of the current scheme above. q(This \(is\) cool) doesn't include the \s in the string because the \ escapes opening delimiters in order to affect matching. So you can have a string q(Open \(paren). Doing something similar with "my" scheme would not work. ): Note that I couldn't find any documentation on this so I resorted to using the Perl debugger to test cases.
- tye (but my friends call me "Tye")In reply to \ in single quotes (Re: DOS directory naming in PERL?)
by tye
in thread DOS directory naming in PERL?
by phathead22
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