From type/Match

See Original text in context

method orig()

Returns the original input to the regex engine, which is usually a string, but doesn't need to be (could be anything that can be coerced to a string):

42 ~~ /.+/;
say $/.orig;            # OUTPUT: «42» 
say $/.orig.^name;      # OUTPUT: «Int»

See #method target for a close equivalent that always returns a string.