Hi,

I have one problem about the backreferences in regular expressions. I learned from the book "Beginning in Perl" (Page 162) that perl has a series of special variables in which it stores anything that is matched with a group in parentheses.Each time it sees a set of parentheses, it copies the matched text inside into a numbered variable- the first matched group goes in $1, the second group in $2 and so on. We call them as backreference variables.

However, when I tried out the following example in the book on my computer (the code is as follows):

#!/usr/bin/perl
use warnings;
use strict;

$_ = 'This is a silly sentence. {3}. 2: but one may find it useful in 
+learning regular expression.';
print "please enter your pattern: "
my $pattern = <STDIN>;
chomp($pattern);
if(/$pattern/)
{
   print "I have found the pattern: ";
   print "\$1 is '$1'\n" if defined $1;
}
else 
{
   print "Sorry, we did not find anything this time.\n";
}

[download]
########## End of the Code ###################

When I enter a word "is" as the pattern, my program only said "I have found the pattern: ", but it did not print out the $1 it is supposed to print out. Can anyone help me out?

Thank you very much for your help in advance! Look forward to your reply soon.

In reply to Please Help: A regular expression problem by PerlMonkJunior

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