How can I use "s" as a substitution delimiter in Perl?

Question

I was playing with Perl and thought that

sssssss

Would have been the same as

s/s/ss/

It seems only certain delimiters can be used. What are they?

Answer 1

You can use any non-whitespace character as the delimiter, but you can't use the delimiter inside PATTERN or REPLACEMENT without escaping it. This is totally valid:

my $x = 's';
$x =~ s s\ss\s\ss;
print $x; # prints "ss"

Note that a space is required after the first s or else it will be interpreted as ss identifier.