To find all elements of an array satisfying a certain condition in Perl, you can use the grep function. The grep function takes a block of code or a subroutine and an array as input, and returns a new array containing the elements of the original array for which the block or subroutine returns true.
Here's an example that demonstrates how to use grep to find all even numbers in an array:
my @numbers = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
my @even_numbers = grep { $_ % 2 == 0 } @numbers;
print "@even_numbers\n"; # prints "2 4 6 8 10"
In this example, we declared an array @numbers containing the numbers 1 through 10. We then called the grep function with a block of code that checks if each element of the array is even ($_ % 2 == 0) and the @numbers array as input.
The grep function returned a new array containing only the even numbers in @numbers, which we assigned to the @even_numbers variable. We then printed this array using the print function.
You can replace the condition in the grep block of code with any other condition that you want to use to filter the array.