sub capture {\@_};
# the eval here returns 1 to make for a cheap check for success.
# we could check $@ but why bother?
sub readonly{ my $v=$_[0]; eval{$_[0]=$v;1} ? 0 : 1 }

$\="\n";
print "No eval        :",readonly(capture(5)->[0]);
eval '
print "In str eval    :",readonly(capture(5)->[0]);
';
eval {
print "In block eval  :",readonly(capture(5)->[0]);
};
print "Block Eval ret :",readonly(eval{capture(5)}->[0]);
print "Str Eval ret   :",readonly(eval'capture(5)'->[0]);

##</code><code>##

No eval        :1
In str eval    :1
In block eval  :1
Block Eval ret :1
Str Eval ret   :0