Using my with parentheses and only one variable

I sometimes see Perl code like this:

my ( $variable ) = blah....

What is the point of putting parentheses around a single variable? I thought parentheses were only used when declaring multiple variables, like:

my ( $var1, $var2, $var3 ) = blah...

Solution 1:

There are several scenarios when there is a difference:

1. When array is on right side

   my @array = ('a', 'b', 'c');
   my  $variable  = @array;           #  3   size of @array
   my ($variable) = @array;           # 'a'  $array[0]
   

2. When list is on right side

   my  $variable  = qw/ a b c d /;    # 'd'  last  item of the list
   my ($variable) = qw/ a b c d /;    # 'a'  first item of the list
   

3. Subroutine with variable (array/scalar) return value

   sub myFunction {
     ...
     return (wantarray() ? @array : $scalar);
   }
   my  $variable  = myFunction(...);  # $scalar   from the subroutine
   my ($variable) = myFunction(...);  # $array[0] from the subroutine
   

Solution 2:

The parentheses create a list context which affects how the right hand side of the assignment is evaluated.

Compare

my $x = grep { /s/ } qw(apples bananas cherries);
print $x;

with

my ($x) = grep { /s/ } qw(apples bananas cherries);
print $x;

You will often use this construction when you just want to grab the first element of a list and discard the rest.