Dear fellow monks,

Please consider the following: 

$code  = 'while (<>) {';
$code .= 'if (/';
$code .= join ('/ && /', @regexen);
$code .= '/) {'
$code .= '   print $_;'
$code .= '}} ';
eval $code;
die "Error: $@\n Code:\n$code\n" if ($@);

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I would like to ask a specific and a general question:

Specifically, I am interested in performance: if matching many patterns, how does qr// + while-loop perform, compared with an eval of a built string containing while-loop + same patterns 'hard-coded' (as in the above example).

And more generally: how do people use eval string? Are there cases that really need it? (but I would also like to invite the more strange uses.)

I do understand that it should only be used on trusted strings.
My experience with eval string is limited, and I hope to learn from the way others are using this clearly powerful technique.

Thanks

In reply to eval string possibilities by erix

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