Re^2: Regex help

Is that documented behaviour? Where?

Yes, in perlre, as follows:

An unescaped "$" or "@" interpolates the corresponding variable, while escaping will cause the literal string "\$" to be matched.

(Though in the version of the perlre man page I have installed, for perl 5.8.8, this sentence comes second in a paragraph that begins with:

You cannot include a literal "$" or "@" within a "\Q" sequence."

I can understand that some might consider this obscure.)

Comment on Re^2: Regex help

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Re^3: Regex help by pKai (Priest) on Jul 26, 2009 at 09:48 UTC
Those remarks in perlre are not specific to character classes, and one regularly thinks these character classes are more special. Explicit mentioning of `$` being special in character classes is found in perlretut#Using-character-classes: …The special characters for a character class are `-]\^$` (and the pattern delimiter, whatever it is). `]` is special because it denotes the end of a character class. `$` is special because it denotes a scalar variable.… So indead not only punctation variables are being expanded: `E:\Temp>perl -Mstrict -we "my $foo=7;die qq(matched '$&'\n) if '123456 +7rab_.'=~/[${foo}bar]+/" matched '7rab'` [download]	[reply] [d/l] [select]

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Re^3: Regex help
by pKai (Priest) on Jul 26, 2009 at 09:48 UTC

Those remarks in perlre are not specific to character classes, and one regularly thinks these character classes are more special.

Explicit mentioning of $ being special in character classes is found in perlretut#Using-character-classes:

…The special characters for a character class are -]\^$ (and the pattern delimiter, whatever it is). ] is special because it denotes the end of a character class. $ is special because it denotes a scalar variable.…

So indead not only punctation variables are being expanded:

E:\Temp>perl -Mstrict -we "my $foo=7;die qq(matched '$&'\n) if '123456
+7rab_.'=~/[${foo}bar]+/"
matched '7rab'
[download]

[reply]
[d/l]
[select]