This expression does not always match. The presence of ^ and $ impose conditions that cause it to not always match. The code below shows a simple case which does not match

$data = "This doesn't match\n";

if ($data =~ /^\s*$/)
{
    print "$data Matches\n";
}
else 
{
    print "$data Does not match\n";
}
#OUTPUT
#This doesn't match
# Does not match
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