Perl: Regex for matching and replacing word and optional full stop

Question

I'm trying to capitalise some file names and also apply some exceptions to it. I have a series of substitutions, of which one is

s/\b(vs|etc)[.]?\b/\L$1./gir

With this I want to match any occurrence of "vs" or "Vs" or "vs." or "VS." or "etc." or "Etc" and so on. If the source string already has a full stop (eg. "Vs.") then I don't want to add one, otherwise I do want to add one. The resulting part of the string also needs to be lowercased, so that the only valid outputs are vs. or etc..

It's probably just a trivial change, but I just can't find it. Can someone let me in on the thought process to assemble the regex, please?

You need to move the word boundary before optional `.`, `s/\b(vs|etc)\b\.?/\L$1./gir` — Wiktor Stribiżew, Sep 20 '21 at 07:29
Thanks. That was one of the attempts I made, but it didn't make a difference in the result. Are you saying that a ```.``` is not counted towards a word? — Alex Ixeras, Sep 20 '21 at 07:31
Right, `\.\b` will only match if there is a letter, digit or `_` right after `.`. — Wiktor Stribiżew, Sep 20 '21 at 07:32

score 2 · Accepted Answer · answered Sep 20 '21 at 07:38

Remember that a word boundary meaning is context-dependent.

Here, you need to move the word boundary before optional . as \.\b (i.e. when there is a . after, say, etc) will only match if there is a letter, digit or _ right after ..

So, you can use

s/\b(vs|etc)\b\.?/\L$1./gir

See the Perl demo online:

#!/usr/bin/perl
use feature 'say';
use strict;
use warnings;

my $str = "vs or Vs or vs. or VS. or etc avs and metch";
say $str =~ s/\b(vs|etc)\b\.?/\L$1./gir;
# => vs. or vs. or vs. or vs. or etc. avs and metch

Perl: Regex for matching and replacing word and optional full stop

1 Answers1