Qwestion about Automatic Match Variables

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

I am using the example program that's in the Learning Perl, 4th Edition

dmathis@radar perl$ cat regexp

#!/usr/bin/perl

while (<>) {                   # take one input line at a time
    chomp;
    if (/(dmathis@gmail.\w+)/) {
        print "Matched: |$`<$&>$'|\n";  # the special match vars
    } else {
        print "No match: |$_|\n";
    }
}
[download]

dmathis@radar perl$ ./regexp

I am using dbmathis@domain.com with this example?
No match: |I am using dbmathis@domain.com with this example?|
I am using dmathis@gmail.org this time.
Matched: |I am using <dmathis@gmail>.org this time.|
[download]

shouldn't the last output be:

Matched: |I am using <dmathis@gmail.org> this time.|

Comment on Qwestion about Automatic Match Variables Select or Download Code

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Re: Qwestion about Automatic Match Variables by Corion (Patriarch) on Sep 22, 2008 at 13:00 UTC
Using warnings or launching `perl` with the `-w` switch would have told you that there is a problem: `> perl -w tmp.pl Possible unintended interpolation of @gmail in string at tmp.pl line 5 +. Name "main::gmail" used only once: possible typo at tmp.pl line 5. Terminating on signal SIGINT(2)` [download] ... and using strict would have prevented that error completely as it forces you to predeclare variables: > type tmp.pl #!/usr/bin/perl use strict; while (<>) { # take one input line at a time chomp; if (/(dmathis@gmail.\w+)/) { print "Matched: \|$`<$&>$'\|\n"; # the special match vars } else { print "No match: \|$_\|\n"; } } > perl -w tmp.pl Possible unintended interpolation of @gmail in string at tmp.pl line 6 +. Global symbol "@gmail" requires explicit package name at tmp.pl line 6 +. Execution of tmp.pl aborted due to compilation errors. [download] You need to escape the `@` because Perl interprets this as the start of the name of an array: `... if (/(dmathis\@gmail.\w+)/) { ...` [download]	[reply] [d/l] [select]
Re^2: Qwestion about Automatic Match Variables by dbmathis (Scribe) on Sep 22, 2008 at 13:39 UTC
lol! That's what I get for copying and pasting :) I always use -w and I just assumed that the code in the book would have it so I never checked. Thanks fo rthe pointer.	[reply]
Re^3: Qwestion about Automatic Match Variables by wol (Hermit) on Sep 22, 2008 at 14:27 UTC
Ah - that would also explain why the example in the book contains your email address. ;-)	[reply]
Re: Qwestion about Automatic Match Variables by wrinkles (Pilgrim) on Sep 22, 2008 at 14:34 UTC
You probably want to escape the '.' to prevent matching typos like 'dmathis@gmail,com' `if (/(dmathis@gmail\.\w+)/) {` [download] Update: Added the escape. Oops! Hitting "Stop" on my browser apparently didn't stop the form from being submitted on my previous post. Next time I'll be patient and let the browser finish loading, then edit the post. :)	[reply] [d/l]
Re: Qwestion about Automatic Match Variables by wrinkles (Pilgrim) on Sep 22, 2008 at 14:33 UTC
You probably want to escape the '.' to prevent matching typos like 'dmathis@gmail,com' `if (/(dmathis@gmail.\w+)/) {` [download]	[reply] [d/l]