Perl complains

Like that?

/tmp>cat at.pl
#!/usr/bin/perl

use strict;
use warnings;
use feature 'say';

say '@foo!';
say "\@bar!";
say "@bang!";

/tmp>perl at.pl
Possible unintended interpolation of @bang in string at at.pl line 9.
Global symbol "@bang" requires explicit package name (did you forget t
+o declare "my @bang"?) at at.pl line 9.
Execution of at.pl aborted due to compilation errors.

/tmp>
[download]

Read the error messages. They are not just decoration. Think about what perl is trying to tell you. Hint: Search for the error messages in perldiag.

Update:

You can have perl do the lookup for you:

/tmp>cat at.pl
#!/usr/bin/perl

use strict;
use warnings;
use diagnostics;
use feature 'say';

say '@foo!';
say "\@bar!";
say "@bang!";

/tmp>perl at.pl
Possible unintended interpolation of @bang in string at at.pl line 10 
+(#1)
    (W ambiguous) You said something like '@foo' in a double-quoted st
+ring
    but there was no array @foo in scope at the time.  If you wanted a
    literal @foo, then write it as \@foo; otherwise find out what happ
+ened
    to the array you apparently lost track of.

Global symbol "@bang" requires explicit package name (did you forget t
+o declare "my @bang"?) at at.pl line 10.
Execution of at.pl aborted due to compilation errors (#2)
    (F) You've said "use strict" or "use strict vars", which indicates
    that all variables must either be lexically scoped (using "my" or 
+"state"),
    declared beforehand using "our", or explicitly qualified to say
    which package the global variable is in (using "::").

Uncaught exception from user code:
        Global symbol "@bang" requires explicit package name (did you 
+forget to declare "my @bang"?) at at.pl line 10.
        Execution of at.pl aborted due to compilation errors.

/tmp>
[download]

Alexander