perl split interesting behavior - perl

Question

can somebody explain this weird behavior:
I hava path in a string and I want to split it for each backslash
my $path = "D:\Folder\AnotherFolder\file.txt";
my #folders = split('\', $path);
in the case above it won't work not even if escaping the backslash like this:
my #folders = split('\\', $path);
but in the case of a regexp it will work:
my #folders = split( /\\/, $path);
why is so?

Answer 1

I think amon gave the best literal answer to your question in his comment:
more explicitly: strings and regexes have different rules for escaping. If a string is used in place of a regex, the string literals suffer from double escaping
Meaning that split '\\' uses a string and split /\\/ uses a regex.
As a practical answer, I wanted to add this:
Perhaps you should consider using a module suited for splitting paths. File::Spec is a core module in Perl 5. And also, you have to escape backslash in a double quoted string, which you have not done. You can also use single quotes, which looks a bit better in my opinion.
use strict;
use warnings;
use Data::Dumper;
use File::Spec;
my $path = 'D:\Folder\AnotherFolder\file.txt'; # note the single quotes
my #elements = File::Spec->splitdir($path);
print Dumper \#elements;
Output:
$VAR1 = [
'D:',
'Folder',
'AnotherFolder',
'file.txt'
];

Answer 2

If you look at the documentation by running:
perldoc -f split
you will see three forms of arguments that split can take:
split /PATTERN/,EXPR,LIMIT
split /PATTERN/,EXPR
split /PATTERN/
This means that even when you pass split a string as the first argument, perl is coercing it into a regex.
If we look at the warnings we get when trying to do something like this in re.pl:
$ my $string_with_backslashes = "Hello\\there\\friend";
Hello\there\friend
$ my #arry = split('\\', $string_with_backslashes);
Compile error: Trailing \ in regex m/\/ at (eval 287) line 6.
we see that first, '\\' is interpolated as a backslash escape followed by an actual backslash, which evaluates to a single backslash.
split then puts the backslash we gave it, and coerces it to a regex as if we had written:
$ my #arry = split(/\/, $string_with_backslashes);
which doesn't work because there is only a single backslash which is interpreted as simply escaping the forward slash after it (without having a terminating /) to show that the regex has ended.

Answer 3

One of the neater ways to extract the elements of a path is to extract all sequences of characters other than a path separator.
use strict;
use warnings;
my $path = 'D:\Folder\AnotherFolder\file.txt';
my #path = $path =~ m([^/\\]+)g;
print "$_\n" for #path;
output
D:
Folder
AnotherFolder
file.txt

Answer 4

When split is used in the form of split STRING and not split REGEX, the string is being converted into a regex. In your case split '\\' will be converted to split /\/ since the first backslash is considered an escape character.
The correct way to do it is split '\\\\' which will be translated to split /\\/.