map { /(\d+)/; $1 }

##</code><code>##

$ perl -le'
use Data::Dumper;
my @y = map { /(\d+)/; $1 } qw/ ab123cd ab456cd abcdefg ab789cd /;
print Dumper \@y;
'
$VAR1 = [
          '123',
          '456',
          undef,
          '789'
        ];

##</code><code>##

$ perl -le'
use Data::Dumper;
my @y = map /(\d+)/, qw/ ab123cd ab456cd abcdefg ab789cd /;
print Dumper \@y;
'
$VAR1 = [
          '123',
          '456',
          '789'
        ];