do is "not really a function". It is a block that
has a seperate scope from wherever it was called from. This
allows you to localize
$/ so that when execution
leaves our "temporary" scope,
$/ will be what it
was before it was changed.
If you look up $/ in perlvar, you will
see
You may set it to a multi-character
string to match a multi-character terminator, or
to "undef" to read through the end of file.
Finally,
<DATA> returns the next line from the
filehandle
DATA, and since
$/ is
undefined, the entire contents of the file are
returned and "caught" in a scalar.
UPDATE: i should add that this is one of those few cases
where
local is a good choice. For example,
local $/;
Is essentially the same as
local $/ = undef;
Which is not the same as
$/ = undef;
Even though that last snippet will be contained inside a
do block ...
$/ will still be
undef afterwards. Try this - make two files
foo.txt and
bar.txt and run this:
# print entire file
open FH,'foo.txt';
my $foo = do {$/ = undef;<FH>};
print $foo;
# print only first line
open FH,'bar.txt';
my $bar = <FH>;
print $bar;
Then go back and add
local to the
do
block.
jeffa
L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)