please guide!!

We did last week: Changing the order of elements in the variable

Having received advice on an almost identical problem, surely you could have at least attempted a solution on your own before asking for help. Please read: How do I post a question effectively?

if($author eq "Cheng, Liying, Fox, Janna., and Zheng, Ying. ") {
  $author = "Liying Cheng, Janna. Fox, Ying. Zheng ";
}
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I have used this code:

$author = "Cheng, Liying, Fox, Janna., Zheng, Ying.";
@author = split(',' , $author);
$length = scalar(@author);
$l = 0;
$j = 1;
for($i=0; $i<$length/2 ; $i++)
{

        $author1[$i]= "$author[$j] $author[$l]";
        $l = $l+2;
        $j = $j+2;
}
$author = join (',' , @author1);
print "$author\n\n";
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but this is not feasible

use strict;
use warnings;

my $author = "Cheng, Liying, Fox, Janna., and Zheng, Ying. "; 

$author =~ s/\.| and| //g;
my %hash = split (',', $author);

my @authors;

for my $key (sort keys %hash) {
    push @authors,"$hash{$key} $key";
}

$author = join(',', @authors);
print "$author\n";
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Liying Cheng,Janna Fox,Ying Zheng
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$author = "$author,";
$author =~ s/(.*?),(.*?),/$2 $1,/g;
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