#! /usr/bin/perl use strict; use warnings;print "\n----------------------------------simple_pattern_Metacharacter_quantifier--------------------------\n";$_ = "asteriskasterisk hash access unpack_func";for (/as.*e/){    print "matched.\n";}for (/(asterisk)+/){    print "matched*2.\n";}for(/unpack.*|lvalue|alignment/){    print "matched*3.\n";}my @escaped = "asteriskasterisk hash access unpack_func";print @escaped;print "@escaped";foreach(@escaped){    print $_;}print "\n";print $escaped[0];print "\n";unless( $escaped[1] ){    print "\$escaped[1] is undef.";}print "\n----------------------------------simple_pattern_Metacharacter_quantifier--------------------------\n";print "\n----------------------------------_alternative_--------------------------\n";print $_."\n";for(/access (unpack|indices)_func/){    print "matched*4.\n";}print "\n----------------------------------_alternative_--------------------------\n";print "\n----------------------------------_character_class--------------------------\n";$_ = ‘z‘;for(/[a-cw-z]/){    print "matched*5.\n";    print "\000";    print "\n";    print "\177";}$_ = "The HAL-9000 requires 8 authorization.";if(/HAL-[0-9]+/){    print "HAL computers mentioned."}print "\n----------------------------------_character_class--------------------------\n";print "\n----------------------------------_character_class_shortcut--------------------------\n";if(/HAL-\d+/){    print "HAL computers mentioned. matched*5.\n";}if(/requires \w authorization/){    print "matched*6.\n";}print "\n----------------------------------_character_class_shortcut--------------------------\n";print "\n----------------------------------exercise_ch7_--------------------------\n";$_ = "aligning Alignrick or veralign.";if(/align/){    print "matched*7.\n";}open ARROW_NOTATION,"< file_4_ex_ch7.txt";my $counter = 8;while(<ARROW_NOTATION>){    chomp;    my $arraow_Syntax = $_;    #for(/[a|A]lign/){    for(/\./){        print "matched*$counter.\n";        $counter++;        print $arraow_Syntax."\n";    }}close ARROW_NOTATION;print "\n----------------------------------exercise_ch7_--------------------------\n";print "\n----------------------------------exercise_ch7_4--------------------------\n";while(<>){    if(/[A-Z][a-z]+/){        print $_."\n" ;    }    if(/[a-z][A-Z]/){        print $_."\n" ;    }}print "\n----------------------------------exercise_ch7_4--------------------------\n";