9.9. Exercises
See Section A.8, "Answers to Chapter 9 Exercises" for answers to the following
exercises:
-
[7] Make a pattern that will match three consecutive copies of
whatever is currently contained in $what. That is,
if $what is fred, your pattern
should match fredfredfred. If
$what is fred|barney, your
pattern should match fredfredbarney or
barneyfredfred or
barneybarneybarney or many other variations.
(Hint: You should set $what at the top of the
pattern test program with a statement like my $what =
'fred|barney';.)
-
[15] Write a program that looks through the
perlfunc.pod file for lines that start with
=item and some whitespace, followed by a Perl
identifier name (made of letters, digits, and underscores, but never
starting with a digit), like the lines below. (There may be more text
on the line after the identifier name; just ignore it.) You can
locate the perlfunc.pod file on your system with
the command perldoc -l perlfunc, or ask your local
expert. (Hint: You'll need the diamond operator to open this
file. How will it get the filename?) Have the program print each
identifier name as it finds it; there will be hundreds of them, and
many will appear more than once in the file.
As an example, the following lines of input resemble what
you'll find in perlfunc.pod. For the first
line, the program should print wilma. For the
second, it should print fred (ignoring the word
flintstone, since we're interested only in
the identifier name):
=item wilma
=item fred flintstone
-
[10] Modify the previous program to list only the identifier names
that appear more than twice on those =item lines,
and tell how many times each one appeared. (That is, we want to know
which identifier names appear on at least three separate
=item lines in the file.) There should be a couple
of dozen, depending upon your version of Perl.
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