3.5. Interpolating Arrays into StringsLike scalars, array values may be interpolated into a double-quoted string. Elements of an array are automatically separated by spaces[79] 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,[80] 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 A single element of an array will be replaced by its value, just 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 Note that 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.[81]
If you want to follow a simple scalar variable with a left square bracket, you need to delimit the square bracket so that it isn't considered part of an array reference, as follows: @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) Copyright © 2002 O'Reilly & Associates. All rights reserved. |
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