What is meant by the pattern space in sed? Briefly describe the fields and associative arrays of awk. In what ways did even early versions of Perl improve on sed and awk? Explain the special...

What is meant by the pattern space in sed? Briefly describe the fields and associative arrays of awk. In what ways did even early versions of Perl improve on sed and awk? Explain the special relationship between while loops and file handles in Perl. What is the meaning of the empty file handle, ?