Regex to match whole word with a particular definition of a word

Question

I am doing a file search and replace for occurrences of specific words in perl. I\'m not usually much of a perl or regex user. I have searched for other regex questions here

Answer 1

Use the \b anchor to match only on a word boundary:

s/\bcat\b/cat_tastic/g

Although Perl has a slightly different definition of what a "word" is. Reading the perlre reference guide a couple of times might help you understand regexps a bit better.

Running perl -pi -e "YOUR_REGEXP" in a terminal and entering in lines of text can help you understand and debug what a particular regexp is doing.

Answer 2

See the example on this page which explains boundary matchers

Enter your regex: \bdog\b
Enter input string to search: The dog plays in the yard.
I found the text "dog" starting at index 4 and ending at index 7.

Enter your regex: \bdog\b
Enter input string to search: The doggie plays in the yard.
No match found.

Answer 3

You could try:

s/([^0-9a-z_])([0-9a-z_]+)([^0-9a-z_])/$1$2_tastic$3/gi

Basically, a non-word character, then a set of word characters, followed by a non-word character. The $1,$2,$3 represent the captured groups, and you replace $2 with $2_suffix.

Hope that helps, not a perl guy buy pretty regex-savvy. Note that the above will fail if the word is the very first or very last thing in a string. Not sure if perl regexen allow the syntax, but if so, fixing the first/last issue could be done with:

s/(^|[^0-9a-z_])([0-9a-z_]+)([^0-9a-z_]|$)/$1$2_tastic$3/gi

Using ^ and $ to match beginning/end of string.