If you wrote the module, why not add a second argument to the getConfigValue() function to act as a default value? Then the check for defined is hidden inside the module and your calling code is as simple as my $value = getConfigValue( "use_foo", 1 );.

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print map { my ($m)=1<<hex($_)&11?' ':'';
$m.=substr('AHJPacehklnorstu',hex($_),1) }
split //,'2fde0abe76c36c914586c';
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