I really don't like to write...

Why not? It can help you remember context of a var and whether or not it may be undefined at that point.

I would use:

if ( defined $foo and $foo ne "bar")
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to remind myself that $foo could be undefined, or, when assigning $foo:

# depending on context
my $foo = whatever() || ''; 
my $foo = whatever() || 0;
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provided $foo as an empty string/zero is not going to cause you problems. If $foo could be valid as either in a comparison, you need to go the define route (or turn off warnings - yuck!).

.02

cLive ;-)