On 10/28/09 Wed Oct 28, 2009 9:37 AM, "Harry Putnam" <rea...@newsguy.com>
scribbled:
>
> What follows is snippet out of a more complex script and reworked to
> simplify but still not seeing what causes the problem.
>
> I'm not sure if I've just stared at it too long or what. When I run it
> I get this error:
>
> Use of uninitialized value in pattern match (m//) at ./match.pl
> line 14. No match here
>
> #!/usr/local/bin/perl
>
> use strict;
> use warnings;
>
> my $date_re = qr/^Date:/;
> my $other_re = qr/^Date: some date/;
>
> if (/$date_re/ !~ /$other_re/){
> print "No match here\n"
> }else{
> print "It's a match\n";
> }
>
The regular expression /$date_re/ by itself with no explicit variable being
bound to it, e.g. $line =~ /$date_re/, will be bound to the global variable
$_, which is the default variable for many Perl operators. Since at the time
your if statement is executed $_ has no value, you get the error message.
Comparing two regular expressions is usually meaningless. You can combine
the results of two regular expression matches using logical operators:
$_ = 'some string';
if( /$date_re/ && !/$other_re/ ) {
# $_ matches $date_re but not $other_re
}
We need to know what you are trying to accomplish here.
--
To unsubscribe, e-mail: beginners-unsubscr...@perl.org
For additional commands, e-mail: beginners-h...@perl.org
http://learn.perl.org/
