How would you know if it's being seen as a string or a number, though? Because once you try to test that, Perl will just Do The Right Thing anyway.

$foo = 0; # Declaring as a number
if ($foo eq '0') {
    print "Oops, it's a string!\n";
}

$foo = "0"; # Declaring as a string
if ($foo == 0) {
    print "Oops, now it's a number!\n";
}
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Bottom line: Perl will always Do The Right Thing when it comes to worrying about stringifying numbers or number-fying strings.