Perl Regex "Not" (negative lookahead)

Question

I'm not terribly certain what the correct wording for this type of regex would be, but basically what I'm trying to do is match any string that starts with "/" but is not followed by "bob/", as an example.

So these would match:

/tom/
/tim/
/steve

But these would not

tom
tim
/bob/

I'm sure the answer is terribly simple, but I had a difficult time searching for "regex not" anywhere. I'm sure there is a fancier word for what I want that would pull good results, but I'm not sure what it would be.

Edit: I've changed the title to indicate the correct name for what I was looking for

TLDR: Negative Lookaheads

If you wanted a negative lookahead just to find "foo" when it isn't followed by "bar"...

$string =~ m/foo(?!bar)/g;

Working Demo Online

Source

To quote the docs...

(?!pattern)

(*nla:pattern)

#(*negative_lookahead:pattern)

A zero-width negative lookahead assertion. For example /foo(?!bar)/ matches any occurrence of "foo" that isn't followed by "bar". Note however that lookahead and lookbehind are NOT the same thing. You cannot use this for lookbehind. (Source: PerlDocs.)

Negative Lookaheads For Your Case

The accepted answer is great, but it leaves no explanation, so let me add one...

/^\/(?!bob\/)/

• ^ — Match only the start of strings.
• \/ — Match the / char, which we need to escape because it is a character in the regex format (i.e. s/find/replacewith/, etc.).
• (?!...) — Do not match if the match is followed by ....
• bob\/ — This is the ... value, don't match bob/', once more, we need to escape the /`.