Adding an "and" before the last element in a comma-interpolated array in Perl - perl

Question

I want to create a subroutine that adds commas to elements and adds an "and" before the last element, e.g., so that "12345" becomes "1, 2, 3, 4, and 5". I know how to add the commas, but the problem is the result I get is "1, 2, 3, 4, and 5," and I don't know how to get rid of the last comma.
sub commas {
my #with_commas;
foreach (#_) {
push (#with_commas, ($_, ", ")); #up to here it's fine
}
splice #with_commas, -2, 1, ("and ", $_[-1]);
#with_commas;
}
As you can probably tell, I'm trying to delete the last element in the new array (#with_commas), since it has the comma appended, and add in the last element in the old array (#_, passed to the sub routine from the main program, with no added comma).
When I run this, the result is, e.g., "1, 2, 3, 4, and 5," -- with the comma at the end. Where is that comma coming from? Only #with_commas was supposed to get the commas.
Any help is appreciated.

Answer 1

sub format_list {
return "" if !#_;
my $last = pop(#_);
return $last if !#_;
return join(', ', #_) . " and " . $last;
}
print format_list(#list), "\n";
This also handles lists with only one element, unlike most of the other answers.

Answer 2

You could use join and modify the last element to include an and:
my #list = 1 .. 5;
$list[-1] = "and $list[-1]" if $#list;
print join ', ', #list;

Answer 3

There is a CPAN module for this, Lingua::Conjunction. I use it myself, and recommend it over rolling your own solution. The usage syntax is very simple:
conjunction(#list);

Answer 4

#!/usr/bin/perl
use warnings;
use strict;
sub commas {
return "" if #_ == 0;
return $_[0] if #_ == 1;
my $last = pop #_;
my $rest = join (", ", #_);
return $rest.", and ".$last;
}
my #a = (1,2,3,4,5);
print commas(#a), "\n";

Answer 5

Add the commas then add the "and ":
use v5.10;
my $string = join ', ', 1 .. 5;
substr
$string,
rindex( $string, ', ' ) + 2,
0,
'and '
;
say $string;
So, work that in as the case when you have more than two elements:
use v5.10;
my #array = 1..5;
my $string = do {
if( #array == 1 ) {
#array[0];
}
elsif( #array == 2 ) {
join ' and ', #array
}
elsif( #array > 2 ) {
my $string = join ', ', #array;
my $commas = $string =~ tr/,//;
substr
$string,
rindex( $string, ', ' ) + 2,
0,
'and '
;
$string;
}
};
say $string;

Answer 6

Just in the spirit of TIMTOWTDI (though, frankly, #perreal's answer is better as far as readability):
sub commas {
my $last_index = $#_;
my #with_commas = map { (($_==$last_index) ? "and " : "") . $_[$_] }
0 .. $last_index;
print join("," #with_commas)
}
This is somewhat similar to Alan's answer (more convoluted/complicated), but the benefit compared to that is that it would work if you need to add "and " to any OTHER element than the last one; Alan's only works when you know the exact offset (e.g. last element)

Answer 7

Small hint
for( 1 .. 10 ) {
print ;
$_ == 10 ? print '' : ($_ != 9 ? print ', ' : print ' and ');
}