I like the matched delimeters; parens, brackets, and braces. They minimize or eliminate backwhacking, which eases the "leaning toothpick" effect. You don't even need to escape the delimeters if their use in your regex is balanced.

Usually s[...][...].

Very occasionally s<...><...>

For me, always balanced for the reasons Zaxo gave , but also because they highlight in a different colour to the contents of the regex and so stand out.

I use the same for all other quote-likes also for consistancy.

I never use a pipe because it's a metacharacter in regular expressions and forces me to parse more carefully as I read the code. Since I want the delimiter to be tall and skinny, if that's possible, the ! bang is my delimiter of choice when the slash won't do. If that still leads to backslashitis, I use pairing delimiters, usually curlies.

I use curly brackets or commas s{ ... }{ ... }g or s, ... , ... ,g;

s:/::;
s!/!!;
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I used to do that, but I find that the hash marks tend to visually “smother” the text they surround, particularly when it is short, as in your example. Try putting several short substitutions like that in a row:

s#foo#bar#g, s#bar#baz#g for @line;
$line[0] =~ s#baz#quux#g;
$line[1] =~ s#qoox#frobble#g;
s#firble#flar#g, s#fooz#bish#g for @line;
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Most people's eyes will glaze over. I know mine do.

Makeshifts last the longest.

Yet another curly user; except on the command line where I tend use "," since it's handy in that perl, zsh, and sed all can deal with it and it stands out fairly well against paths (e.g. !!:gs,/home/fletch/,/usr/local/,).