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Postings from July 2003
Ed Christian wrote:
> I assumed that, $1 would be reset (either undefined or set to null)
> once I exited the scope of the while loop my regexp was called in.
> Sadly, I was mistaken. :) Below is a test example of code I wrote,
> with $1 values differing from those I expected. Do I need to
> explicitly set $1..$n to an empty string before every regexp if I'm
> to test based on the results of that regexp?
>
> Thanks!
> - Ed
>
> -=-=-=-=-=-
> #!/usr/bin/perl -w
> use strict;
> use warnings;
>
> while (<DATA>) {
> chomp;
> /(\d+)/;
> print "\$1: $1\n";
> }
> __DATA__
> 1
> 2
> a
> 3
>
>
> Expected results:
> $1: 1
> $1: 2
> $1: # <--- was expecting an empty string
> $1: 3
You've already gotten the answer on how $1 works. But, if you want to get
undef on a failed match, you can use the match in a list context:
my ($number) = /(\d+)/;
Now $number will contain the matched string, or undef if there was no match.
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