What the heck does this mean?

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

            if(  m#^coclli=(.*)# && $coclli eq "" ) {
               $coclli = $1;
               }
[download]

I have inherited a piece of code that "supposedly" works.

There are no variables or subroutines named m. What hould this code do? I see it as m then a comment for the rest of the line. Any ideas?

Thanks

Edit 2001-03-12 by tye

Comment on What the heck does this mean? Download Code

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Re: What the heck does this mean? by japhy (Canon) on Mar 13, 2001 at 01:28 UTC
Running it through the deparser, I get: `if (/^coclli=(.*)/ and $coclli eq '') { $coclli = $1; }` [download] It's using a regex to assign to `$coclli` if the variable isn't already assigned. The deparser is available in Perl 5.005 and up, as: `japhy% perl -MO=Deparse program_name` [download] `japhy` -- Perl and Regex Hacker	[reply] [d/l] [select]
Re: Re: What the heck does this mean? by Falkkin (Chaplain) on Mar 13, 2001 at 01:33 UTC
Basically, in English, this code reduces to: If the string `$_` starts with "coclli=", and then "some characters", and the variable `$coclli` is equal to the empty string, set the variable `$coclli` to the (any-amount-of-characters).	[reply] [d/l] [select]
Re: What the heck does this mean? by myocom (Deacon) on Mar 13, 2001 at 01:33 UTC
`perldoc -f m` tells you to look at the perlop manpage. In short, it's the match operator.	[reply] [d/l]
Re: What the heck does this mean? by vonman (Acolyte) on Mar 13, 2001 at 01:29 UTC
There should be a newline after the eq"")and the $1;. Txs	[reply]
Re: What the heck does this mean? by vonman (Acolyte) on Mar 13, 2001 at 01:34 UTC
I think what is happening is that the original code must not be displaying characters correctly on my machine. So what should I replace m and # with?	[reply]
Re: Re: What the heck does this mean? by japhy (Canon) on Mar 13, 2001 at 01:36 UTC
What are you talking about? `m//` is the pattern match operator, and you can use characters other than `/` for the delimiter. Thus, the code can be: `/^coclli=(.)/ # or m!^coclli=(.)! # or m<^coclli=(.*)>` [download] Perl can be as eccentric as the programmers who use it. `japhy` -- Perl and Regex Hacker	[reply] [d/l]
Re: Re: What the heck does this mean? by astanley (Beadle) on Mar 13, 2001 at 02:24 UTC
perl allows you to specify any character as the regexp seperator. / is just a suggestion and I guess is most widely used? Either way the perldocs say you can use m## just as easy as m// if, for instance you wanted to match a string that had a lot of /'s in it and didn't want to \/ them all - m#///# would work and is a little easier to read than m/\/\/\//. Adam	[reply]


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