C:\>perl -e "use 5.012; my $foo='abc def';my @foo=split(/ /,$foo); for
+ (@foo) {say $_;}
abc
def

C:\>perl -e "use 5.012; my $foo='abc def';my @foo=split m/ /,$foo; for
+ (@foo) {say $_;}
abc
def
[download]

What did I miss?

That split(/ /,$foo) and split m/ /,$foo are exactly the same.    I was pointing out the difference between split m/ /, $line and split(" ", $line)

$ perl -le'
use Data::Dumper;
$Data::Dumper::Useqq = 1;
my $foo = "  abc\t\tdef\r\rghi\n";
print Dumper $_ for split / /, $foo;
'
$VAR1 = "";

$VAR1 = "";

$VAR1 = "abc\t\tdef\r\rghi\n";

$ perl -le'
use Data::Dumper;
$Data::Dumper::Useqq = 1;
my $foo = "  abc\t\tdef\r\rghi\n";
print Dumper $_ for split " ", $foo;
'
$VAR1 = "abc";

$VAR1 = "def";

$VAR1 = "ghi";
[download]

What did I miss?

If you use -E instead of -e, you can save yourself from typing use 5.012; :)

C:\test>perl -E "my $foo='abc def';my @foo=split m/ /,$foo; for (@foo)
+ {say $_}"
abc
def
[download]

A little more by omitting the $_:

C:\test>perl -E "my $foo='abc def';my @foo=split m/ /,$foo; for (@foo)
+ {say}"
abc
def
[download]

More still by using the modifier form of for:

C:\test>perl -E "my $foo='abc def';my @foo=split m/ /,$foo; say for @f
+oo"
abc
def
[download]

A lot more by using the string constant directly in the only place it is used:

C:\test>perl -E "my @foo=split m/ /,'abc def'; say for @foo"
abc
def
[download]

And finally, do away with the variables completely:

C:\test>perl -E "say for split m/ /,'abc def'"
abc
def
[download]

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.