3.5. Interpolating Arrays into Strings Like scalars,array values may be interpolated into a double-quoted string. Elements of an array are automatically separated by spaces upon interpolation:
@rocks = qw{ flintstone slate rubble };
print "quartz @rocks limestone/n"; # prints five rocks separated by spaces
There are no extra spaces added before or after an interpolated array; if you want those,you'll have to put them in yourself: print "Three rocks are: @rocks./n";
print "There's nothing in the parens (@empty) here./n";
If you forget that arrays interpolate like this,you'll be surprised when you put an email address into a double-quoted string. For historical reasons, this is a fatal error at compile time:
$email = "fred@bedrock.edu"; # WRONG! Tries to interpolate @bedrock
$email = "fred/@bedrock.edu"; # Correct
$email = 'fred@bedrock.edu'; # Another way to do that
However,in versions of Perl 5 soon to be released as we write this,the behavior of an unseen array variable will become similar to an unseen scalar variable,i.e.,replaced with an empty string with a warning if warnings are enabled. The Perl developers apparently figure that 10 years of fatality are enough warning. A single element of an array will be replaced by its value as you'd expect: @fred = qw(hello dolly);
$y = 2;
$x = "This is $fred[1]'s place"; # "This is dolly's place"
$x = "This is $fred[$y-1]'s place"; # same thing
The index expression is evaluated as an ordinary expression,as if it were outside a string. It is not variable interpolated first. In other words,if $y contains the string "2*4",we're still talking about element 1,not element 7,because "2*4" as a number (the value of $y used in a numeric expression) is just plain 2. If you want to follow a simple scalar variable with a left square bracket,you need to delimit the square bracket so it isn't considered part of an array reference:
@fred = qw(eating rocks is wrong);
$fred = "right"; # we are trying to say "this is right[3]"
print "this is $fred[3]/n"; # prints "wrong" using $fred[3]
print "this is ${fred}[3]/n"; # prints "right" (protected by braces)
print "this is $fred"."[3]/n"; # right again (different string)
print "this is $fred/[3]/n"; # right again (backslash hides it)
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