Re: Negating a leading whitespace

icg,
If I understand correctly, you want to do something with a line if it contains 2 characters but exclude it if they are preceded by a whitespace. Negated character classes to the rescue:

if ( $line =~ /[^\s]XY/ ) { ... }
[download]

Where XY are the two characters you want. Alternatively, if the whitespace requirement for exclusion is at the beginning of the line you can just do:

while ( <FILE> ) {
    next if /^\s/;
    # process lines without leading whitespace here ...
}
[download]

Cheers - L~R

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Re^2: Negating a leading whitespace by Roy Johnson (Monsignor) on Jul 05, 2005 at 15:23 UTC
Your first example wouldn't match a line that began with XY, because it requires some character to precede it. Negative lookbehind or an alternation would fix: `/(?:^\|\S)XY/ # or /(?<!\s)XY/` [download] (I also prefer the builtin not-whitespace char, rather than negating the class). Caution: Contents may have been coded under pressure.	[reply] [d/l]
Re^2: Negating a leading whitespace by davidrw (Prior) on Jul 05, 2005 at 15:30 UTC
I believe OP wants to check for the 2 chars _anywhere_ in the string, as long as the line doesn't start w/whitespace (so your second method)... I think this is easiest w/just two checks (i was having trouble making a single regex w/look-behinds): `if ( $line =~ /^\S/ && $line =~ /XY/ ){ ... }` [download] Unless you can assume that the 2 chars will never be at the beginning of the line, in which case you can just do: `if ( $line =~ /^\S.*?XY/ ){ ... }` [download]	[reply] [d/l] [select]