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How do I pass more than one array or hash to a subroutine

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Contributed by vroom on Jan 18, 2000 at 23:10 UTC
Q&A  > subroutines


Answer: How do I pass more than one array or hash to a subroutine
contributed by hossman

If you declare your subroutine with a function prototype specifying each argument as \% or \@, then your method will automatically get a reference to the hashes/arrays passed to it, without the person calling the function/method/subroutine needing to do anything special.

Note that, like all prototypes, this doesn't work when calling the subroutine using & or as a method.

See the 'Prototypes' section of perlsub for more details, or this node for a good example.

Answer: How do I pass more than one array or hash to a subroutine
contributed by vroom

You need to pass these by reference, otherwise Perl will not see each array or hash as distinct.

You can create a reference by simply prefixing a variable with \ like so:

processarrays(\@array1, \@array2); processhashes(\%hash1, \%hash2);
To use them inside of their routines you can do stuff like the following:
$sub processarrays{ my($a1, $a2) = @_; foreach(@$a1){ # dereferences $a1 print $_; } for($i=0; $i<@$a2; $i++){ print $a2->[$i]; #get at a particular index within array } } sub processhashes{ my($h1,$h2)=@_; foreach my $key(keys %$h1){ #derefences $h1; print $h1->{$key}; #lookup based on $key } }

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