I've talked about the Scalar::Util module before, and once again it comes to the rescue! 
use Scalar::Util qw(readonly);
...
if (readonly $x) {
  ...
}

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Get used to Scalar::Util and List::Util now - they're standard modules in 5.8.

In reply to Re: Re: How could I check if a variable is 'read-only'? by robin
in thread How could I check if a variable is 'read-only'? by vladb

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