Re: Comparing two variables when one variable includes a regexp...

Your problem appears to be that $NetPattern doesn't contain the slashes you think it does. You have two choices:

$NetPattern = qr{mbist[\w+\d+\/]*\[\d+\]}x;
if ($NetName =~  $NetPattern) {# Do fantastical things...}
[download]

$NetPattern = 'mbist[\w+\d+\/]*\[\d+\]';
if ($NetName =~ qr/$NetPattern/x) {# Do fantastical things...}
[download]

The "" style quotes interpolated your slashes away.

The qr is also most useful (in my opinion) for precompiling regular expressions, so I would choose the first solution, particularly if you have a lot of matches to do on that single regular expression. It's also nice for being able to tell that $NetPattern is of type Regexp. So, I guess there's also this third choice...

$NetPattern = 'mbist[\w+\d+\/]*\[\d+\]';
if ($NetName =~ m/$NetPattern/x) {# Do fantastical things...}
[download]

-Paul

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Re^2: Comparing two variables when one variable includes a regexp... by Narveson (Chaplain) on May 01, 2008 at 18:25 UTC
Surely all these replies that fix one example out of an infinite number of possible user inputs are missing the point? If I understood the original post, `$NetPattern` is to be read from the command line, so the example, mistaken bracketing and all, was just an example. The question was If a user enters a command-line regular expression that gets pushed into a variable, what is the most reliable way to use that variable to compare it against another variable that is a string? In our answers, we should be explaining how to validate a user-supplied string before interpolating it into a regex. A simple error like `[` without matching `]` is the least of our worries.	[reply] [d/l] [select]
Re^3: Comparing two variables when one variable includes a regexp... by jettero (Monsignor) on May 01, 2008 at 19:24 UTC
That's an excellent point actually. I'll amend my answer, although I covered it somewhat. Assuming you actually trust the user, this seems like a sane way to do it. `my $regexp = <$file_handle>; my $creg = eval { qr($regexp) }; if( $@ ) { warn "regex error: $@"; } else { if( $something =~ $creg ) { # do wonderful things. } }` [download] I apparently skipped the meat of the question because it seemed clear to me that the reason the matching failed was because of an interpolation problem with a test regexp that he generated between quotes and he wasn't actually reading it from the user -- which would have likely worked the way he had it. -Paul	[reply] [d/l]