Context

In a reciprocal fashion, an operation provides either a scalar or a list context to each of its arguments. For example, if you say

    int( <STDIN> )

the integer operation provides a scalar context for the < STDIN> operator, which responds by reading one line from STDIN and passing it back to the integer operation, which will then find the integer value of that line and return that. If, on the other hand, you say

    sort( <STDIN> )

then the sort operation provides a list context for < STDIN>, which will proceed to read every line available up to the end of file, and pass that list of lines back to the sort routine, which will then sort those lines and return them as a list to whatever the context of the sort was.

Assignment is a little bit special in that it uses its left argument to determine the context for the right argument. Assignment to a scalar evaluates the righthand side in a scalar context, while assignment to an array or array slice evaluates the righthand side in a list context. Assignment to a list also evaluates the righthand side in a list context.

User defined subroutines may choose to care whether they are being called in a scalar or list context, but most subroutines do not need to care, because scalars are automatically interpolated into lists. See wantarray.