Just use the name of the hash in scalar context, such as 

if (%foo) {
    # %foo has at least one key
} else {
    # %foo has no keys
}

[download]

If you want to be very explicit, you can also write 

if (!!%foo) { ... }

[download]
or 
if (scalar %foo) { ... }

[download]
or 
if (0+%foo) { ... }

[download]

In reply to Re: How to check whether a hash is empty (has no keys)? by ambrus
in thread How to check whether a hash is empty (has no keys)? by ambrus

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