Re: regex problem

Well, there are two differences between your examples -- the use of variables and the switch from !~ to =~. Is the latter a typo? ~~If not, then you can accomplish the same thing by using [^$pattern].~~ In any case, your real question is whether regexes can be constructed, and the answer is yes. It's simply a matter of writing it as a normal string, and using perlfunc:eval to compile at runtime. (Note, you may have to do some character escaping (using '\') in your original string if it gets at all complicated.) For example: my $string = "$foo|$bar"; for ( list ) { eval !~ /$string/; }

As far as expense goes, I can't see any reason why this would be particularly taxing.

Update Juerd++ for the correction regarding [^$pattern]. My mistake.

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Re: Re: regex problem by Juerd (Abbot) on Feb 09, 2002 at 21:49 UTC
If not, then you can accomplish the same thing by using `[^$pattern]`. `[^$pattern]` is misleading. `[]` create a character class, so `[^$characters]` would be a good example. That doesn't negate a regex, though. It's simply a matter of writing it as a normal string, and using perlfunc:eval to compile at runtime. That requires parsing. Parsing is bad, because it's too easy to do it the wrong way. This too doesn't really answer the question. `eval !~ /$string/;` Unless you meant `eval($_) !~ /$string/;`, and I'm sure you didn't, that's wrong. `2;0 juerd@ouranos:~$ perl -e'undef christmas' Segmentation fault 2;139 juerd@ouranos:~$` [download]	[reply] [d/l] [select]

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Re: Re: regex problem
by Juerd (Abbot) on Feb 09, 2002 at 21:49 UTC

If not, then you can accomplish the same thing by using [^$pattern].

[^$pattern] is misleading. [] create a character class, so [^$characters] would be a good example. That doesn't negate a regex, though.

It's simply a matter of writing it as a normal string, and using perlfunc:eval to compile at runtime.

That requires parsing. Parsing is bad, because it's too easy to do it the wrong way. This too doesn't really answer the question.

eval !~ /$string/;

Unless you meant eval($_) !~ /$string/;, and I'm sure you didn't, that's wrong.

2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$
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