Regular Expression Longest Possible Matching

Question

So I have an input string which is a directory addres:

Example: ProgramFiles/Micro/Telephone

And I want to match it against a list of words very strictly:

Example: Tel|Tele|Telephone

I want to match against Telephone and not Tel. Right now my reg looks like this:

my( $output ) = ( $input =~ m/($list)/o );

The regex above will match against Tel. What can I do to fix it?

Answer 1

If you want a whole word match:

\b(Tel|Tele|Telephone)\b

\b is a zero-width word boundary. Word boundary in this case means the transition from or to a word character. A word character (\w) is [0-9a-zA-Z_].

If you simply want to match against the longest in a partial word match put the longest first. For example:

\b(Telephone|Tele|Tel)

or

(Telephone|Tele|Tel)

Answer 2

Change the orders: Tel|Tele|Telephone to Telephone|Tele|Tel. By the regexp algorithm, alternation is searched from left-to-right, if there found a match, that's it, no greedy matching. For example: /a|ab|abc/ working on "abc" matches "a" instead of the most greedy "abc".

or use the matching expressions.

Tel(?:e(?:phone)?)?