Answer by Sobrique for How to replace special characters to underscore(_) perl

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 perluse 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.