davorg presents the common idiom, but note that it can lose if the actual value returned is "defined but false", e.g. 0 or "0". To handle this robustly can be done in two lines: 
$CONFIG{HASHTYPE} = $cfg->val("MISC","HASHTYPE");
$CONFIG{HASHTYPE} = "shal" if ! defined $CONFIG{HASHTYPE};

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In reply to Re: How to deal with undefined returned variables. by knight
in thread How to deal with undefined returned variables. by Pug

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