JSON expects double quotes. So, replacing the double quotes should work. Maybe you care to show us the code you used to replace the single quotes with double quotes?

Thanks a lot everyone, both solution works. I'll use  $response =~s/[{:,]\K(\w+)(?=[:,}])/"$1"/g; to limit module usage, but PP is fine.

What's wrong with using a module, and why would you rather do it wrong? (Your thing won't work if any string contains a double quote, for example.)

alert( JSON.stringify({Id:'343410466704417574',Pseudo:"LRYWLL",Country
+:'PERL_REPUBLIC',CountryId:1,Can:'true'}) )
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Thanks but I can't use JS in my program.
I Easly replaced every single quotes by double quotes with $response =~ s/'/"/g; Now how can I do with a regex :
Quote every unquoted characteres beetween { or , or :
and { or , or :
Can I capture matching string with ( ) and use it in the replace part of the regex with quote around ?
I tried with

$response =~s/({|,|:)(.+)(}|,|:)/"$&"/g;
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But it quotes the whole JSON...

What about

quote: 'He said: "boo!"'
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Can I capture matching string with ( ) and use it in the replace part of the regex with quote around ?

$1

>perl -le"$_='abc'; s/(.)/[$1]/sg; print"
[a][b][c]
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Thanks but I can't use JS in my program.

Maybe you should insist on JSON :D