WarrenBullockIII has asked for the wisdom of the Perl Monks concerning the following question:

I have this code that I took out of Learning Perl. In this example I used the while loop to check that my input with the regular expression. However, why is it that when I take the while loop away and try alternate methods of comparing data to the regular expression it will not compile it gives me a message that says: ---use of uninitialized value in pattern match (m//) What are alternate methods of comparing a value to the regular expression in the if statement??? 
#!/usr/bin/perl -w

use strict;

#get the user input first
print "type a string: ";
while(<>){
chomp();

if(/Wilma.*Fred|Fred.*Wilma/){
print "$_\n";
}
else{
print "\n\nyour line was skipped because it did not mention Fred and W
+ilma\n\n";
}
}

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Edit by tye

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Re: While loop and pattern match (was Re: need help)
by VSarkiss (Monsignor) on Jun 05, 2002 at 22:33 UTC

    Both your while loop and your pattern match are using $_ implicitly. This line: while (<>) {is equivalent to: while (defined($_ = <>)) {Similarly, if (/foo/) {is equivalent to: if ($_ =~ /foo/) {Change to using an explicit variable and you should be OK. Look at perlsyn for more details.

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      thanks VSarkiss
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        Or you can keep the implicit match, if you add the explicit assignement to $_ before. :-) Which sometimes makes the code briefer and therefor easier to read, and sometimes makes it too short in the wrong place and therefor harder to read. (As a beginner, you should probably stick to the explicit syntax for a while.)

        Makeshifts last the longest.

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