If you have an end delimiter and you want to allow this end delimiter to appear literally you need to escape it, hence \' => '

But if you're escaping, you're also needing an escape character, which has also to be escaped when used literally, hence \\ => \

And thats it, nothing else needed within the single quotes family of q{} with a free choice of end delimiters.

And now, if you think that perl sucks try emacs lisp, which only supports double quotes! In elisp regexes suffer from a ugly disease called slasheritis².

Luckily you can use heredocs, because there is no delimiter that need to be escaped. And if you don't like the newlines then chomp:

$foo = <<'__HERE__';
\\some.address.or.whatever\subdir\
__HERE__
chomp $foo;
print ">", $foo ,"<";             # >\\some.address.or.whatever\subdir
+\<
[download]

I suppose you don't wanna put multiple path in a long heredoc? ¹

So why don't you use a character like / as placeholder?

sub s2b {   # slash to backslash
  (my $str = shift) =~ tr#/#\\#;
  return $str;
}
 
my $path = s2b '//some.address.or.whatever/subdir/';
[download]

Just don't blame Perl for M$ decision to use an escape character for separating paths. =)

update

fixed code for s2b()

footnotes

¹) you could read them into a hash defined by preceded hash keys.

use Data::Dump;

sub parsepath {
  my $str=shift;
  return split /\s+/,$str;
}

my %path = parsepath <<'__HERE__';
install    \\some.address.or.whatever\subdir\
deinstall  \\other.address.or.whatever\subdir\
__HERE__

dd \%path;
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==>

{
  deinstall => "\\\\other.address.or.whatever\\subdir\\",
  install   => "\\\\some.address.or.whatever\\subdir\\",
}
[download]

²) yes, it insults the eyes!!!