How to replace special characters to underscore(_) perl

my @folder = ('s,c%','c__pp_p','Monday_øå_Tuesday,  Wednesday','Monday &       Tuesday','Monday_Tuesday___Wednesday');

if ($folder =~ s/[^w_*-]/_/g ) {
  $folder =~ s/_+/_/g;
  print "$folder : Got %n" ; 
}

Using above code i am not able to handle this “Monday_øå_Tuesday_Wednesday”

The output should be :

s_c
c_pp_p
Monday_øå_Tuesday_Wednesday
Monday_Tuesday
Monday_Tuesday_Wednesday

Answer

You can use W to negate the w character class, but the problem you’ve got is that w doesn’t match your non-ascii letters.

So you need to do something like this instead:

#!/usr/bin/env perl
use strict;
use warnings;
use Data::Dumper;

my @folder = ('s,c%','c__pp_p','Monday_øå_Tuesday,  Wednesday','Monday &       Tuesday','Monday_Tuesday___Wednesday');

s/[^p{Alpha}]+/_/g for @folder;
print Dumper @folder;

Outputs:

$VAR1 = [
          's_c_',
          'c_pp_p',
          'Monday_øå_Tuesday_Wednesday',
          'Monday_Tuesday',
          'Monday_Tuesday_Wednesday'
        ];

This uses a unicode property – these are documented in perldoc perluniprop – but the long and short of it is, p{Alpha} is the unicode alphanumeric set, so much like w but internationalised.

Although, it does have a trailing _ on the first line. From your description, that seems to be what you wanted. If not, then… it’s probably easier to:

s/_$// for @folder;

than make a more complicated pattern.