$ perl -le'
my $x = "1234 abcd 5678";
print $& if $x =~ /[a-z]+/;
print $& if $x =~ //;
print map qq[ "$_"], split /[a-z]+/, $x;
print map qq[ "$_"], split //, $x;
'
abcd
abcd
 "1234 " " 5678"
 "1" "2" "3" "4" " " "a" "b" "c" "d" " " "5" "6" "7" "8"