Understand that, as far as perl is concerned, passing an array or a hash is the same as passing a list of values. This is known as list context.

# functionally speaking, this....
%hash = ('a' => 1, 'b' => 2, 'c' => 3);
myfunc(%hash);

# is the same as this...
myfunc('a', 1, 'b', 2, 'c', 3);
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So you'll either want to put the scalar value first and shift it off:

$scalar = 'blue';
%hash = ('a' => 1, 'b' => 2);
myfunc($scalar, %hash);

sub myfunc {
  my $scalar = shift;
  my %hash = @_;
  print $hash{'a'};
}
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Or pass arrays and hashes by reference, because when you pass a reference to an array or hash, the reference is a scalar context.

%hash = ('a' => 1, 'b' => 2);
$scalar = 'blue';
myfunc(\%hash, $scalar);

sub myfunc {
  my($hashref,$scalar) = @_;
  print $hashref->{'a'};
}
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