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Dereferencing in Perl
Dereferencing in Perl returns the value from a reference point to the location. To dereference a reference simply use $, @ or % as a prefix of the reference variable depending on whether the reference is pointing to a scalar, array, or hash. Following is the example to explain the concept −
Example
#!/usr/bin/perl $var = 10; # Now $r has reference to $var scalar. $r = \$var; # Print value available at the location stored in $r. print "Value of $var is : ", $$r, "\n"; @var = (1, 2, 3); # Now $r has reference to @var array. $r = \@var; # Print values available at the location stored in $r. print "Value of @var is : ", @$r, "\n"; %var = ('key1' => 10, 'key2' => 20); # Now $r has reference to %var hash. $r = \%var; # Print values available at the location stored in $r. print "Value of %var is : ", %$r, "\n";
Output
When the above program is executed, it produces the following result −
Value of 10 is : 10 Value of 1 2 3 is : 123 Value of %var is : key220key110
If you are not sure about a variable type, then it's easy to know its type using ref, which returns one of the following strings if its argument is a reference. Otherwise, it returns false −
SCALAR ARRAY HASH CODE GLOB REF
Example
Let's try the following example −
#!/usr/bin/perl $var = 10; $r = \$var; print "Reference type in r : ", ref($r), "\n"; @var = (1, 2, 3); $r = \@var; print "Reference type in r : ", ref($r), "\n"; %var = ('key1' => 10, 'key2' => 20); $r = \%var; print "Reference type in r : ", ref($r), "\n";
Output
When the above program is executed, it produces the following result −
Reference type in r : SCALAR Reference type in r : ARRAY Reference type in r : HASH
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