Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!mit-eddie!uw-beaver!ubc-cs!phillips
From: phillips@cs.ubc.ca (George Phillips)
Newsgroups: comp.lang.perl
Subject: Re: Is this a Bug?
Summary: yes
Keywords: perl bug
Message-ID: <9888@ubc-cs.UUCP>
Date: 5 Oct 90 18:45:14 GMT
References: <9134@cg-atla.UUCP>
Sender: news@cs.ubc.ca
Organization: University of British Columbia, Vancouver, B.C., Canada
Lines: 32

In article <9134@cg-atla.UUCP> white@cg-atla.UUCP (Frank ) writes:
>
>	I am using 'perl' PL18. Running the following script
>causes "WORD WITH PARENS" to be printed. What's the difference?
>----------------- cut here -------------------------------------------
>#!/usr/local/bin/perl
>
>$_ = "This line contains a\nword beginning a line";
>if ( /^word/ ) {
>	print "WORD NO PARENS\n";
>} elsif ( /^(word)/ ) {
>	print "WORD WITH PARENS\n";	# I get this message !!
>}

Yep, this is a bug.  There's even a passage in the manual page which
says, more or less, that ^ does not necessarily work as advertised.
If you're using ^ in a regular expression and you're not sure if
the string has a newline in it, you'd better do something like:

if (/^regexp/ && $` eq "") { # yep, it really did do an anchored match

So here is a fixed version of your script:

$_ = "This line contains a\nword beginning a line";
if ( /^word/ ) {
   print "WORD NO PARENS\n";
} elsif ( /^(word)/ && $` eq "" ) {
   print "WORD WITH PARENS\n"; # I get this message !!
}

--
George Phillips phillips@cs.ubc.ca {alberta,uw-beaver,uunet}!ubc-cs!phillips