Consider the following code:
$x=1;
$y=1;
$x++ , $y++ if 0; # note the comma! both x and y are one statement
print "With comma: $x $y\n";
$x=1;
$y=1;
$x++ ; $y++ if 0; # note the semicolon! so two separate statements
print "With semicolon: $x $y\n";
The output is as follows:
With comma: 1 1
With semicolon: 2 1
A comma is similar to a semicolon, except that both sides of the command are treated as a single statement. This means that in a situation where only one statement is expected, both sides of the comma are evaluated.
This is an important note, thank you