I have an array like this:
my @array = qw( zero one two three four five six seven eigth nine);
How to output a subarray consisting of strings of length 4 from @array. For example, if the string is equal to 4, the new array will be output as @subarray = ( zero four five nine )
The built-in function grep serves as the "filter" operation in Perl, capable of filtering a list based on a regular expression or an arbitrary block.
If given a block, grep will call the block for each element of the list, setting the implicit variable $_ to the current value. It will keep the values which return truthy. So your filter would look like
my @subarray = grep { length == 4 } @array;
length, like a lot of built-in Perl functions, can take an argument (length($a), etc.), but when called without one it automatically takes the implicit variable $_ as an argument.
You can also pass it a regular expression. This is mainly useful if you're worried your coworkers like you too much and want to make some enemies.
my @subarray = grep(/^.{4}$/, @array);
length is like querying of what?
$_ in perlvar for a long list of things that take $_ as their default