use strict;
use warnings;

my @match = map { /(2)/ ? $1 : () } 0..9;
print scalar @match, "\n"; # is 1, no grep required

@match = map { /(2)/ } 0..9;
print scalar @match, "\n"; # is 1

@match = map { $1 if /(2)/ } 0..9;
print scalar @match, "\n"; # is 10

@match = grep { defined } map { $1 if /(2)/ } 0..9;
print scalar @match, "\n"; # is 10

@match = grep { length } map { $1 if /(2)/ } 0..9;
print scalar @match, "\n"; # is 1