Perl | my keyword

my keyword in Perl declares the listed variable to be local to the enclosing block in which it is defined. The purpose of my is to define static scoping. This can be used to use the same variable name multiple times but with different values.

Note: To specify more than one variable under my keyword, parentheses are used.

Syntax: my variable

Parameter:
variable: to be defined as local

Returns:
does not return any value.

Example 1:

#!/usr/bin/perl -w

# Local variable outside of subroutine
my $string = "Geeks for Geeks";
print "$string\n";

# Subroutine call
my_func();
print "$string\n";

# defining subroutine
sub my_func
{
    # Local variable inside the subroutine
    my $string = "This is in Function";
    print "$string\n";
    mysub();
}

# defining subroutine to show
# the local effect of my keyword
sub mysub
{
    print "$string\n";
}

Output:

Geeks for Geeks
This is in Function
Geeks for Geeks
Geeks for Geeks

Example 2:

#!/usr/bin/perl -w

# Local variable outside of subroutine
my $string = "Welcome to Geeks";
print "$string\n";

# Subroutine call
my_func();
print "$string\n";

# defining subroutine
sub my_func
{
    # Local variable inside the subroutine
    my $string = "Let's GO Geeky!!!";
    print "$string\n";
    mysub();
}

# defining subroutine to show
# the local effect of my keyword
sub mysub
{
    print "$string\n";
}

Output:

Welcome to Geeks
Let's GO Geeky!!!
Welcome to Geeks
Welcome to Geeks

How to define dynamic scoping?
The opposite of “my” is “local”. The local keyword defines dynamic scoping.

# A perl code to demonstrate dynamic scoping
$x = 10;
sub f
{
   return $x;
}
sub g
{
   # Since local is used, x uses
   # dynamic scoping.
   local $x = 20;

   return f();
}

print g()."\n";