---input---
str.gsub(%r{\\\\}, "/")

---tokens---
'str'         Name
'.'           Operator
'gsub'        Name
'('           Punctuation
'%r{'         Literal.String.Regex
'\\\\'        Literal.String.Regex
'\\\\'        Literal.String.Regex
'}'           Literal.String.Regex
','           Punctuation
' '           Text.Whitespace
'"'           Literal.String.Double
'/'           Literal.String.Double
'"'           Literal.String.Double
')'           Punctuation
'\n'          Text.Whitespace