in reply to Re^3: About a piece of code
in thread About a piece of code

\s is the single space ' ' character. In your set [ \t\n\r\f] that thing right before the \t is \s.

Oooh I see now... in a character set [\s\t\f\r\n], \s means a single space.
in a regex \s means all of the chars in this set: [\s\t\f\r\n]. Yep, confusing!!
\s has a context dependent meaning. Such as it is.

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Re^5: About a piece of code
by jwkrahn (Abbot) on Aug 05, 2009 at 19:10 UTC

    \s is not a single character in a regular expression, it is the character class [ \t\n\r\f].   See perlre. 

    $ perl -le'
 use Data::Dumper;
 $Data::Dumper::Useqq = 1;
 print Dumper grep /\s/, map chr, 0 .. 255;
'
$VAR1 = "\t";
$VAR2 = "\n";
$VAR3 = "\f";
$VAR4 = "\r";
$VAR5 = " ";

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    In a double quoted string it is just the character "s". 

    $ perl -le'
 use Data::Dumper;
 $Data::Dumper::Useqq = 1;
 print Dumper "\s";
'
$VAR1 = "s";

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Re^5: About a piece of code
by JadeNB (Chaplain) on Aug 05, 2009 at 21:57 UTC
    I think that, since the common regex wisdom involves replacing a literal space in an /x-modified regex with \s, it's easy to think of \s as a replacement for a literal space—but, if you actually want a literal space (rather than just a single whitespace character) in such a regex, but outside a character class, then what you want is '\' (i.e., an escaped space).
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