比较运算符 #

my $a = 10;
my $b = 20;

if ($a == $b) {
    print "Equal\n";
}

if ($a != $b) {
    print "Not equal\n";
}

if ($a < $b) {
    print "$a is less than $b\n";
}

if ($a >= 5) {
    print "$a is greater or equal to 5\n";
}

my $result1 = 5 <=> 10;
my $result2 = 10 <=> 10;
my $result3 = 15 <=> 10;

print "$result1, $result2, $result3\n";

my @numbers = (5, 2, 8, 1, 9, 3);
my @sorted = sort { $a <=> $b } @numbers;
print "@sorted\n";

my $str1 = "apple";
my $str2 = "banana";

if ($str1 eq $str2) {
    print "Equal\n";
}

if ($str1 ne $str2) {
    print "Not equal\n";
}

if ($str1 lt $str2) {
    print "$str1 comes before $str2\n";
}

my $result1 = "apple" cmp "banana";
my $result2 = "apple" cmp "apple";
my $result3 = "banana" cmp "apple";

print "$result1, $result2, $result3\n";

my @words = qw(banana Apple cherry);
my @sorted = sort { $a cmp $b } @words;
print "@sorted\n";

my @sorted_ci = sort { lc($a) cmp lc($b) } @words;
print "@sorted_ci\n";

my $a = "10";
my $b = "2";

if ($a > $b) {
    print "Numeric: 10 > 2\n";
}

if ($a gt $b) {
    print "String: 10 gt 2\n";
}

my $age = "25";

if ($age == 25) {
    print "Age is 25\n";
}

my $name = "Tom";

if ($name eq "Tom") {
    print "Name is Tom\n";
}

use v5.10;

my $value = 42;

if ($value ~~ 42) {
    print "Matches 42\n";
}

my @arr = (1, 2, 3, 4, 5);
if ($value ~~ @arr) {
    print "Found in array\n";
}

my %hash = (a => 1, b => 2);
if ("a" ~~ %hash) {
    print "Key exists\n";
}

my $var;

if (defined $var) {
    print "Defined\n";
} else {
    print "Undefined\n";
}

$var = "";
if (defined $var) {
    print "Defined (empty string)\n";
}

my %hash = (a => 1, b => undef);

if (exists $hash{a}) {
    print "Key 'a' exists\n";
}

if (exists $hash{b}) {
    print "Key 'b' exists\n";
}

if (exists $hash{c}) {
    print "Key 'c' exists\n";
} else {
    print "Key 'c' does not exist\n";
}

my %hash = (a => undef);

print "exists: ", exists $hash{a} ? "yes" : "no", "\n";
print "defined: ", defined $hash{a} ? "yes" : "no", "\n";
print "true: ", $hash{a} ? "yes" : "no", "\n";

sub in_range {
    my ($value, $min, $max) = @_;
    return $value >= $min && $value <= $max;
}

print in_range(5, 1, 10) ? "Yes\n" : "No\n";
print in_range(15, 1, 10) ? "Yes\n" : "No\n";

my $input = "Hello123";

if ($input =~ /^\d+$/) {
    print "All digits\n";
} elsif ($input =~ /^[a-zA-Z]+$/) {
    print "All letters\n";
} else {
    print "Mixed content\n";
}

use version;

my $v1 = version->parse("1.2.3");
my $v2 = version->parse("1.10.0");

if ($v1 < $v2) {
    print "$v1 is older than $v2\n";
}

#!/usr/bin/perl
use strict;
use warnings;
use v5.10;

my $score = 85;
my $grade;

if ($score >= 90) {
    $grade = "A";
} elsif ($score >= 80) {
    $grade = "B";
} elsif ($score >= 70) {
    $grade = "C";
} elsif ($score >= 60) {
    $grade = "D";
} else {
    $grade = "F";
}

say "Score: $score, Grade: $grade";

#!/usr/bin/perl
use strict;
use warnings;
use v5.10;

my @words = qw(Perl Python Ruby PHP JavaScript);

my @sorted_asc = sort { $a cmp $b } @words;
my @sorted_desc = sort { $b cmp $a } @words;
my @sorted_len = sort { length($a) <=> length($b) } @words;

say "Original: @words";
say "Ascending: @sorted_asc";
say "Descending: @sorted_desc";
say "By length: @sorted_len";

#!/usr/bin/perl
use strict;
use warnings;
use v5.10;

my ($username, $password) = ("admin", "secret");

if ($username eq "admin" && $password eq "secret") {
    say "Login successful";
} elsif ($username ne "admin") {
    say "Invalid username";
} else {
    say "Invalid password";
}