While what you have works (shift removes an element from the @_ array), a more normal sort of thing would be like below.

In the first line of the sub, assign local names to the input parameters by putting them into a list context with parens and assigning @_ to that. This is helpful as documentation of the interface - the main thing a caller would need to know is right there on that one line (assuming that we've got some good names).

It is possible to just de-reference the hash_ref which avoids having to make a local copy of the hash (if the hash is big, this will speed things up considerably).

#!/usr/bin/perl -w
use strict;
use Data::Dumper;  # a core module (no installation needed)

my %hash = ( a=> 11, b=>22);
my $value = ("something");

marine ($value, \%hash);

sub marine 
{
   my ($line, $hash_ref) = @_;  # parens needed for list context
   
   print "$line\n";
   print "hash value of key a is $hash_ref->{a}\n"; #no local copy
   
   my %local_hash_copy = %$hash_ref;  #makes complete local copy
   
   print Dumper \%local_hash_copy;
   
}
__END__
something
hash value of key a is 11
$VAR1 = {
          'a' => 11,
          'b' => 22
        };
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