Re: Regex error when [] occurs in file..

in reply to Regex error when [] occurs in file..

$temp =~ s/#$'//; I'm not even sure what you want that to do, but it constructs a regex out of # followed by whatever was followed by the previous match. Any regex special characters in that generated string will be interpreted as regex directives.

You probably want something like:

while (chomp(my $temp=<INPUT>)){
    print Dumper $temp;
    $temp =~ s/#.*//;  # remove comments
    if ($temp =~ /^\s*$/){
        next;
    }
    print "after regex:\n";
    print Dumper $temp;
    print "end\n";
}
[download]

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Comment on Re: Regex error when [] occurs in file.. Select or Download Code

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Re^2: Regex error when [] occurs in file.. by why_bird (Pilgrim) on Mar 03, 2008 at 16:03 UTC
Thanks both---I didn't realise that $' was treated like that. Are all 'special variables' ($&, $N (N is integer)) expanded in that way too? So if you did something like: `$temp =~ m/(\[0-9\])blah$1/;` [download] would you match `$temp = "[0-9]blah6";` [download] rather than `$temp = "[0-9]blah[0-9]";` [download] ? V. interesting---I assumed that special characters inside the rest of the data would be ignored.. Cheers <--edit to make the last sentence make more sense!--> ........ Those are my principles. If you don't like them I have others. -- Groucho Marx .......	[reply] [d/l] [select]
Re^3: Regex error when [] occurs in file.. by Joost (Canon) on Mar 03, 2008 at 16:11 UTC
Are all 'special variables' ($&, $N (N is integer)) expanded in that way too? All variables are expanded that way, special or not: `my $var = '[ab]'; my $string = '12a3434'; print "match" if $string =~ /$var/;` [download] See also quotemeta and the \Q and \E escape sequences. "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply] [d/l]
Re^3: Regex error when [] occurs in file.. ($1 vs. \1) by almut (Canon) on Mar 03, 2008 at 16:31 UTC
`$temp =~ m/(\[0-9\])blah$1/;` [download] I think you meant `$temp =~ m/(\[0-9\])blah\1/;` [download] in which case any special characters in the content of the backreference `\1` would not be treated special. IOW, `"[0-9]blah[0-9]"` would match, but not `"[0-9]blah6"`: `#!/usr/bin/perl use strict; use warnings; for my $temp ("[0-9]blah[0-9]", "[0-9]blah6") { printf "%-15s ", $temp; if ($temp =~ /(\[0-9\])blah\1/) { print "matched\n"; } else { print "didn't match\n"; } }` [download] prints `[0-9]blah[0-9] matched [0-9]blah6 didn't match` [download] while, if you replace `\1` with `$1` in the above regex, it prints `Use of uninitialized value in concatenation (.) or string at ./671663. +pl line 8. [0-9]blah[0-9] matched [0-9]blah6 matched` [download] This is because `$1` isn't defined here, thus the regex effectively becomes `/(\[0-9\])blah/`... Update: added demo code.	[reply] [d/l] [select]

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