Postfixes

Postfix operators are unary operators placed after their single operand.

++ is a postfix increment. The change of the value happens after the current value is used in the expression.

my $x = 42;
say $x++; # 42
say $x;   # 43

-- is a postfix decrement.

Both postfix and prefix operators magically know how to deal with numbers in filenames.

my $filename = 'file01.txt';
for 1..10 {
    say $filename++;
}

This example prints the list of the filenames with incrementing numbers: file01.txt, file02.txt, … file10.txt.

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