Control flow

# block statement

#!/usr/bin/perl -w
{
    print "hello, world\n";
    $a = 0;
    $a++;
    $a++;
    $a++;
    print "\$a = $a\n";
}

# if statement

#!/usr/bin/perl -w
# $a = 0;
$a = 1;
if ($a == 0) {
    print "In loop: \$a = $a\n";
}

# one-line if statement

#!/usr/bin/perl -w
$a = 1;
print "In loop: \$a = $a\n" if ($a > 0);

# unless statement

#!/usr/bin/perl -w
# $a = 0;
$a = 1;
unless ($a == 0) {
    print "In loop: \$a = $a\n";
}

# while statement

#!/usr/bin/perl -w
$a = 0;
while ($a <= 10) {
    print "In loop: \$a = $a\n";
    $a++;
}

# until statement

#!/usr/bin/perl -w
$a = 10;
until ($a <= 0) {
    print "In loop: \$a = $a\n";
    $a--;
}

# do { } while

#!/usr/bin/perl -w
$a = 0;
do {
    print "In loop: \$a = $a\n";
    $a++;
} while ($a <= 10);

# for loop

#!/usr/bin/perl -w
$a = -1;
# print "Before entering: \$a = $a\n";
for ($a = 0; $a <= 10; $a++) {
    print "In loop: \$a = $a\n";
}
# print "Free at last: \$a = $a\n";

# foreach

#!/usr/bin/perl -w
$a = -1;
# print "Before entering: \$a = $a\n";
foreach $a (0 .. 10) {
    print "In loop: \$a = $a\n";
}
# print "Free at last:\$a = $a\n";

Works also with arrays: foreach $i (@array) 

# last statement

#!/usr/bin/perl -w
for ($a = 0; $a <= 10; $a++) {
    last if ($a == 5);
    print "In loop: \$a = $a\n";
}

# next statement

#!/usr/bin/perl -w
for ($a = 0; $a <= 10; $a++) {
    next if ($a == 5);
    print "In loop: \$a = $a\n";
}

# redo statement

#!/usr/bin/perl -w
for ($a = 0; $a <= 10; $a++) {
    redo if ($a == 5);
    print "In loop: \$a = $a\n";
}

# cat.pl

#!/usr/bin/perl -w
while (<>) {
    print;
}

# cat2.pl

#!/usr/bin/perl -w
print while (<>);