POSIX::Run::Capture runs an external command and captures its output.
Both standard error and output are captured.  Upon exit, their contents
can be accessed line by line or in one chunk.  Callback routines can be
supplied that will be called for each complete line of output read,
providing a way for synchronous processing.  Standard input can be
supplied as either a file handle or a text.

This module is for those who value performance and effectiveness over
portability.  As its name suggests, it can be used only on POSIX systems.