You should always check to see if your capture matched anything before using it. 

if ( $2 ) {
    ...
} else {
    ...
}

[download]

Edit: ... By which I do not mean to suggest that you should always use an explicit if conditional: as my learned colleague explains below, there are any number of reasons you might get an undefined value. The point is your code should be ready for it, whether with an explicit test, no warnings, or howsoever you deem best.

The way forward always starts with a minimal test.

In reply to Re: On error, how to show the regexp values? by 1nickt
in thread Tracing warnings: how to show the regexp values? by nikolay

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