On Mon, 19 Sep 2005, John Rudd wrote:
Right, that's the same as what $& is doing: it's telling you what part of the
There is a large performance penalty using the special $` $' $& variables,
because if you use those variables anywhere in the code, they are
propagated for each regex, which is not so for $1 variables.
There was a thread some time ago claiming that e.g. SpamAssassine's huge
amount of regex's drop the performance significantly.
($& is not so problematic than $`and $', if I remember correctly. Perl
developers have made the same quirk, see "perldoc English" last
paragraphe:
"PERFORMANCE
This module can provoke sizeable inefficiencies for regular expres-
sions, due to unfortunate implementation details. If performance
mat-
ters in your application and you don't need $PREMATCH, $MATCH, or
$POSTMATCH, try doing
use English qw( -no_match_vars ) ;
. It is especially important to do this in modules to avoid
penalizing
all applications which use them."
)
Bye,
--
Steffen Kaiser
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