Why is the list my Perl map returns just 1's?

Question

The code I wrote is as below :

#!/usr/bin/perl 

my @input = ( \"a.txt\" , \"b.txt\" , \"c.txt\" ) ;
my @output = map { $_ =~ s/\\..*$// } @input ;

print @o         


        

Answer 1

The problem: both the s/../.../ operator and Perl's map are imperative, expecting you to want to modify each input item; Perl doesn't in fact have a builtin for the functional map that yields its results without modifying the input.

When using s, an option is to append the r modifier:

#!/usr/bin/perl 

my @input = ( "a.txt" , "b.txt" , "c.txt" ) ;
my @output = map { s/\..*$//r } @input ;

print join(' ', @output), "\n";

The general solution (suggested by derobert) is to use List::MoreUtils::apply:

#!/usr/bin/perl 

use List::MoreUtils qw(apply);

my @input = ( "a.txt" , "b.txt" , "c.txt" ) ;
my @output = apply { s/\..*$// } @input ;

print join(' ', @output), "\n";

or copy its definition into your code:

sub apply (&@) {
    my $action = shift;
    &$action foreach my @values = @_;
    wantarray ? @values : $values[-1];
}