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What's wrong with always quoting "$vars"?



Jasmine
Administrator

Jan 19, 2001, 3:01 PM


Views: 3562
What's wrong with always quoting "$vars"?

(From the Perl FAQ)

What's wrong with always quoting "$vars"?

The problem is that those double-quotes force stringification, coercing numbers and references into strings, even when you don't want them to be.

If you get used to writing odd things like these:

Code
    print "$var";       # BAD 
$new = "$old"; # BAD
somefunc("$var"); # BAD

You'll be in trouble. Those should (in 99.8% of the cases) be the simpler and more direct:

Code
    print $var; 
$new = $old;
somefunc($var);

Otherwise, besides slowing you down, you're going to break code when the thing in the scalar is actually neither a string nor a number, but a reference:

Code
    func(\@array); 
sub func {
my $aref = shift;
my $oref = "$aref"; # WRONG
}

You can also get into subtle problems on those few operations in Perl that actually do care about the difference between a string and a number, such as the magical ++ autoincrement operator or the syscall() function.

Stringification also destroys arrays.

Code
    @lines = `command`; 
print "@lines"; # WRONG - extra blanks
print @lines; # right