This is a FAQ.

Thanks you very much, thanks all of you, it's working properly. And thanks for the welcome!

Wow almost I forget.What is this advice: Smartmatch is experimental. What does mean?

It means that the ~~ operator's behaviour might change in a future release, or it could be completely removed. You shouldn't rely on it in production code. Fortunately, there're alternatives listed in the FAQ.
لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

my %answer =  map {$_, 1} (
        "Bad",
        "Good",
        "Not good enough"
);
chomp(my $user_answer=<STDIN>);
if (defined $answer{$user_answer}) {
       print "Ok\n";
}
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my @answer=(
        "Bad",
        "Good",
        "Not good enough"
);
chomp(my $user_answer=<STDIN>);

if (grep (/\b$user_answer\b/, @answer)){
       print "Ok\n";
}
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I tried putting Ba and doesn't match as you said, actually for me it's working, but I will considere your answer/reflexion for future codes. Thanks

I was meaning that with out the \b (to escape word boundaries) "Ba" would match Bad meaning




$match = 'Ba';
@array = ('Bad','Good','Whatever');

if (grep(/$match/, @array)) { print "Yippie!\n"; }
else { print "No Match\n"; }
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If you enclosed the variable $match in word boundaries as followed

grep(/\b$match\b/, @array)


It would no longer match do to the fact that the match must match the exact string passed

My 2-cents worth....
Before I discovered smart matching I used to just loop the array and search for a match.
After reading these answers I thought hey maybe I could use 'join'.
In the code below I have 6 methods including smart match ~~ as proof-of-concept.
I run each of the 6 methods on 3 different match variables.
-- sorry about the golf-style code, it's just how I roll --

my$match,$res;
my@array=("Nice","Bad","Good","Not good enough");

foreach$match("Ba","bad","Bad"){
 
 #method submitted by edimusrex using greb with \b boundaries
 if(grep(/\b$match\b/,@array)){$res="y"}else{$res="n"}
 print"1: $match : $res\n";

 #similar as first method but using ^ start and $ finish matching
 if(grep(/^$match$/,@array)){$res="y"}else{$res="n"}
 print"2: $match : $res\n";

 #smart matching just for POC
 if($match~~@array){$res="y"}else{$res="n"}
 print"3: $match : $res\n";

 #the long method I used to use looping the array
 $res="n";
 foreach(@array){if($_ eq $match){$res="y"}}
 print"4: $match : $res\n";
 
 #joining the array and adding ~ to start and finish as boundaries
 if(("~".join("~",@array)."~")=~/~$match~/){$res="y"}else{$res="n"}
 print"5: $match : $res\n";

 #same as above but using \b boundaries instead of hard-coding ~
 if(join("~",@array)=~/\b$match\b/){$res="y"}else{$res="n"}
 print"6: $match : $res\n\n";

}
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results (perl v5.24.0 on Win7) :

1: Ba : n
2: Ba : n
3: Ba : n
4: Ba : n
5: Ba : n
6: Ba : n

1: bad : n
2: bad : n
3: bad : n
4: bad : n
5: bad : n
6: bad : n

1: Bad : y
2: Bad : y
3: Bad : y
4: Bad : y
5: Bad : y
6: Bad : y
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my$match,$res;
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my has higher precedence than comma, so $res is an undeclared variable there. And since you're not using strict, why bother declaring at all?

I thought my$match,$res; the same as writing

my$match;
my$res;
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I'm just declaring both on one line.
Anyway it was just a rough (working) code fart. If I was gonna bother with strict then I'd even add the shebang! and a "use warning" , but yeah nah, point taken. I'll leave out the local or global declarations next time to make it more obvious, cheers -SJ-