Larry was trained as a missionary and educated as a linguist. He came to language development with the perspective of a linguist. This is why Perl has context and pronouns.
There's a scalar vs. list context when calling a subroutine. Some Perl builtins return different things in the different contexts. Your subroutines can as well, for example by using wantarray() in your code. For example, in list context returning an array or assigning an array to something copies the array. In scalar context an array's value is its number of elements. The readline operator reads a line from the file with file $filehandle in either context. However, in scalar context it reads the "next line" (depending on line ending settings and seeks and such). In list context it reads and returns the list of lines in the file. This has the great benefit that a while loop with reads one line at a time into memory and sets a variable (either one you specify or by default $_) to the line just read. A foreach loop with reads all the lines into memory then operates on them, which is sometimes preferable.
There are operators for numbers and for strings and a single scalar variable can be accessed in either context. This allows for easy coercion from the string "42" to the numeric value 42 or back. It's possible with some trickery to set these two values independently, but don't do that.
There are the pronouns $_ and _ which recall the most recent subject in some situations. There's a magic array @_ which is the list of arguments passed to a subroutine or method. There are match variables for regular expressions, which refer back to the matches. There are the variables $a and $b which are reserved "magic" variables used to support user-defined comparator blocks for the built-in sort(). There are variables for which line of an input file you just read.