Shell Programming and Scripting

$var=A,B,C,D,E,F,G,H

$var=A,B,C, D,E,F, G,H

 
$ perl a.pl 
A,B,C, D,E,F, G,H
 
$ cat a.pl
#!/bin/perl -w
$var="A,B,C,D,E,F,G,H";
@splitArray=split(/,/,$var);
for($i=0;$i<=scalar(@splitArray);$i=$i+3)
{
        if ($i==0) {next;}
        $splitArray[$i]=" " . $splitArray[$i];
}
print join (",",@splitArray);

case 1:

input : $var="A,B,C"   //Only 3 alphabets

output: A,B,C,  // comma not reqd at the end

expected : A,B,C

case2:

input : $var="A,B,C,D,E,F"  // 6 alphabets

output: A,B,C, D,E,F,  // comma not reqd at the end

expected : A,B,C, D,E,F  // a white space after 3 alphabets

case 3: 

input : $var="A,B,C,D,E,F,G,H" // not a multiple of 3

output: A,B,C, D,E,F, G,H  // coming as expected

expected : same as output

$ cat script.pl
use warnings;
use strict;

while ( my $var = <DATA> ) {
        chomp $var;
        $var =~ s/((?:[[:upper:]],){3})(?!$)/$1 /g;
        printf qq[%s\n], $var;
}

__DATA__
A,B,C,D,E,F,G,H
A,B,C
A,B,C,D,E,F
$ perl script.pl
A,B,C, D,E,F, G,H
A,B,C
A,B,C, D,E,F