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Today someone asked about what the following code is doing:
my ($foo, $bar) = @{shift(@_)}{qw/ -foo -bar /};

I thought it's a good idea to add the explanation to the above idiom to the tutorial. (Although tye probably thinks that this is a bad idiom. :-)

What the above code is doing:
shift(@_) # get an element from the parameter list qw/ -foo -bar / # creates a list of two strings: "-foo" and "-bar" @{ shift(@_) }{ qw/ -foo -bar / } # dereference the anonymous hash reference as a hash slice # returns a list containing the values of the given keys # in the anonymous hash, in the form of: # # @values = @hash{@keys} my ($foo, $bar) = @{ shift(@_) }{ qw/ -foo -bar / }; # assign the two element list retrieved into $foo and $bar

This technique can be used to retrieve named parameters in a subroutine. For example:
foobar({ -foo => 'FOO', -bar => 'BAR' }); sub foobar { my ($foo, $bar) = @{shift(@_)}{qw/ -foo -bar /}; print "\$foo => $foo, \$bar => $bar\n"; }

Which I think is pretty handy.


In reply to Perl Idioms Explained - my ($foo, $bar) = @{shift(@_)}{qw/ -foo -bar /} by Roger

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