How to remove all . from string except the last? - perl

Question

I would like to remove all . from a string except from the last.
It can be done in JavaScript like so
var s='1.2.3.4';
s=s.split('.');
s.splice(s.length-1,0,'.');
s.join('');
but when try the same in Perl
my #parts = split /./, $s;
my #a = splice #parts, $#parts-1,0;
$s = join "", #a;
I get
Modification of non-creatable array value attempted, subscript -2 at ./test.pl line 15.
Question
Can anyone figure out how to do this in Perl?

Answer 1

I would use a regexp with positive look-ahead in perl for the task:
perl -pe 's/\.(?=.*\.)//g' <<<"1.2.3.4"
Result:
123.4
EDIT to add a fix to your solution using split:
use warnings;
use strict;
my $s = '1.2.3.4';
my #parts = split /\./, $s;
$s = join( "", #parts[0 .. $#parts-1] ) . '.' . $parts[$#parts];
printf "$s\n";

Answer 2

First of all, escape the dot in split instruction: my #parts = split /\./, $s;

Answer 3

Your split is using a regex /./, in which case . is considered the wild card character. If you want to split on a literal period, you need to escape it:
... split /\./, $s;
splice takes arguments ARRAY or EXPR, OFFSET, LENGTH, LIST (perl v5.14). If LENGTH is 0, nothing is removed, and so nothing is returned.
Your code is contradictory to what you say you are trying to do, so I'm not quite sure what it really is you're trying to do, but assuming you want to remove all periods except the last, I would expect you'd do something like:
my #parts = split /\./, $s;
my $end = pop #parts;
$s = join "", #parts, ".$end";
Or perhaps manipulate the split
my #parts = split /\./, $s;
my $limit = #parts - 1; # the field count for split
$s = join "", split /\./, $s, $limit;
So basically, find out how many fields your string will be split into, subtract one, then perform a new split and set the LIMIT to that.

Answer 4

when in doubt, use diagnostics;
$ perl -Mdiagnostics -le " splice #ARGV, -1 ,0 "
Modification of non-creatable array value attempted, subscript -1 at -e line 1 (#1)
(F) You tried to make an array value spring into existence, and the
subscript was probably negative, even counting from end of the array
backwards.
Uncaught exception from user code:
Modification of non-creatable array value attempted, subscript -1 at -e line 1.
at -e line 1.
$ perl -Mdiagnostics -le " splice #ARGV, -1 ,0 " argv now not empty
I doubt you want to use negative offsets, I think you want to use offset 0 and size of array minus one (also known as the last index )
$ perl -le " print for splice #ARGV, 0, $#ARGV-1 " a b c
a
Ooops. $#ARGV is the last index, not $#ARGV -1, so
$ perl -le " print for splice #ARGV, 0, $#ARGV " a b c
a
b
but if you still want some arithmetic you can use #ARGV, cause in scalar context its the size of the array
$ perl -le " print for splice #ARGV, 0, #ARGV-1 " a b c
a
b
Side-benefit of using non-negative offsets with splice? It doesn't die when array is empty
$ perl -le " print for splice #ARGV, 0, 10 "

Answer 5

This looks more like what you were trying to do in Perl
my #parts = split /\./, $s;
$s = join('', splice(#parts, 0, -1)) . '.' . $parts[-1];

Answer 6

You missed the '.' off your splice call. Here's how it should look
use strict;
use warnings;
my $s = '1.2.3.4';
my #parts = split /\./, $s;
splice #parts, -1, 0, '.';
$s = join "", #parts;

Answer 7

The first argument of split is a regular expression. In regular expressions, "." means "match any character" (with /s) or "match any character except LF" (without /s). You need to escape it to match a literal ".".
my #parts = split(/\./, $s, -1); # "-1" to handle "1.2.3.4."
splice(#parts, -1, 0, '.') if #parts > 2; # "if" to handle "1234"
$s = join('', #parts);
A substitution could do it as well:
$s =~ s/\.(?=.*\.)//sg;