If you want to check whether that particular scalar is defined or not.You can simply use it in the if statement as follows. 
if($scalar)
{
statements
}
else {
statements
}

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If you want to check if it is undef,then you can use unless or simple else for the above if statement. For inverse of if,you can also use unless.

In reply to Re: scalar values assignment by nvivek
in thread scalar values assignment by gogoglou

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