Why "Global symbol require explicit package name"

Hello guy!

I would like to know why I need to declare global variables with "my".

My script looks something like thing:
Use strict;
$strg = "A string";
$strg2 = "a second string";

I get a warning:
"Global symbol require explicit package name."

unless I declare the variables like: 
my $strg = "A string";
my $strg2 = "a second string";

Thanks

• Why "Global symbol require explicit package name" by Babale Fongo
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• Re: Why "Global symbol require explicit package name" by Paul Johnson
• Re: Why "Global symbol require explicit package name" by George Schlossnagle