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### Re^2: Modification of a read-only value attempted

by panku (Initiate)
 on Nov 27, 2012 at 13:34 UTC ( #1005857=note: print w/ replies, xml ) Need Help??

Thanks for the Reply. Please clarify one more doubt. 1.) \$c=99; Here \$c is var which is holding 99 as value. We can change \$c here ? 2.) \$c=\99; Here also \$c is reference which is pointing to 99. So why we can't change \$c=1000? Thanks in advance

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Re^3: Modification of a read-only value attempted
by roboticus (Chancellor) on Nov 27, 2012 at 13:48 UTC

You can change \$c=1000. What you can't do is change 99 to 1000. When you use \$c=1000, it tells perl that \$c is no longer pointing to a reference to the constant 99, but is now containing the value 1000. When you use \$\$c=1000, you're telling perl to change the thing \$c points to to 1000. But \$c points to the constant value 99. Perl is telling you that it refuses to break the time-space continuum by making 99 be 1000.

...roboticus

When your only tool is a hammer, all problems look like your thumb.

Re^3: Modification of a read-only value attempted
by BrowserUk (Pope) on Nov 27, 2012 at 13:57 UTC
So why we can't change \$c=1000?

As roboticus points out, you can make that change. That is, you can overwrite the value in \$c -- currently the address of the constant 99 -- with any other value.

What you cannot do is overwrite the value held at the address held in \$c, because it is a constant.

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