This seems to do what you want.

use strict;
use warnings;

my $str = "'abc', 'dec'f', ''ghc''";
print qq{$str\n};

$str =
   join q{ },
   map  {s{(?<!\A)'(?!\z)}{\\'}g; $_}
   split m{\s*,\s*}, $str;

print qq{$str\n};
[download]

Output is

'abc', 'dec'f', ''ghc''
'abc' 'dec\'f' '\'ghc\''
[download]

Cheers,

JohnGG