You've confused the m//atching operator for a regular expression, a regular expression goes inside the m//atching operator

## matching operator
$var =~ m{};
$var =~ m//;
$var =~ //;
## matching against default variable, against $_
m{};
m//;
//;
[download]

So when your program gets the string  "^atlas\S+/ || /\/world\s+/ || /\nowhere\s+" its not a very good regular expression, it has all these extra | and /